DMLT (2nd Year) : Chemistry of Proteins - Some basic concepts (U. P. State Medical Faculty syllabus) in English & Hinglish

Proteins chemistry - structure, functions, amino acids structure & classification, essential amino acids, zwitterions, protein structure, tests of proteins/amino acids, Biuret test, xanthoproteic acid test, Millon's test, Hopkins-Cole test, nitroprusside test, ninhydrin test, enzymes, isoenzymes, biochemical markers of myocardial injury.

1. 1
DMLT2ndYEAR-SOMEBASICCONCEPTSOFBIOCHEMISTRY(U.P.StateMedical
Facultysyllabus)inEnglish&Hinglish
LESSON3
[ChemistryofProteins]
INENGLISH
CHEMISTRYOFPROTEINS
Whatareproteins-Proteinsarefoundinlargeamountsandindifferentvarietiesinallcellsof
ourbody.Proteinsarepolymersofaminoacidsconsistingofthesamesetof20aminoacidsin
manydifferentcombinationsandsequences.Eachaminoacidresidueisjoinedtoits
neighboringaminoacidbyaspecifictypeofcovalentbondcalled'peptidebond'.
Someimportantfunctionsofproteinsinourbody:
●Theproteinswhichactascatalystsarecalledenzymesandtheseenzymesaccelerate
variousbiochemicalreactions.
●Proteinsarestructuralcomponentsofcellmembranes.
●Someproteinshelpintransportprocessese.g.transportoflipidsbylipoproteinsand
transportofoxygenbyhemoglobin.
●Someproteinshelpinthebodydefencesysteme.g.antibodies.
●Proteinsalsoactasreceptorstorecognisechemicalmessengers.
●Somechemicalmessengersareproteins(hormones).
●Proteinsprovidestructuralsupportandmovementofthehumanbodye.g.proteinfibres
ofconnectivetissuesandmuscles.
Aminoacids-
Twentydifferentaminoacidsarecommonlyfoundinproteins.Theasparaginewasthefirstto
bediscoveredandthreoninewasthelastone.
Commonstructuralfeatures-Aminoacidsareorganiccompoundshavinganacidiccarboxyl
group(-COOH)andabasicaminogroup(-NH2)bondedtothesamecarbonatom(theα
carbon),thecarbonnexttocarboxylcarbon.Inaddition,thereisasidechainorRgroup,
specificforeachaminoacid,whichvaryinstructure,size,andelectriccharge,anditinfluences
thesolubilityoftheaminoacidsinwater.
Theformulaofageneralaminoacid-isRCH(NH2)COOH.
Allaminoacidsexceptglycinehavetwoenantiomers(D-andL-forms,mirrorimageofeach
other).Thisisbecauseallthecommonaminoacidsexceptglycine,havetheαcarbonbonded
tofourdifferentgroups(chiralcarbon)-acarboxylgroup,anaminogroup,anRgroup,anda
hydrogenatom(inglycine,theRgroupisanotherhydrogen).Theconfigurationofthese
stereoisomersisrelatedtotheconfigurationofD-andL-glyceraldehyde.L-Aminoacidsare

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thosewiththeα-aminogroupontheleft,andD-aminoacidshavetheα-aminogrouponthe
right.
Aminoacidsinwater(neutralpH)existasdipolarions(zwitterions)whichactaseitheranacid
orabase.Inthedipolarform,theaminogroupisprotonated(NH3+)andthecarboxylgroupis
deprotonated(COO–).Suchsubstanceshavingthisdual(acid-base)natureareamphotericand
areoftencalledampholytes.TheionizationstateofanaminoacidvarieswithpHofthesolution.
ThepHcanaffectthechargeofamoleculebyintroducingprotons(H+).Theaminogroupofan
aminoacidisaveryeffectiveprotonacceptor,soisconsideredtobebasic.Thecarboxylgroup
isaneffectiveprotondonorandisconsideredtobeacidic.Everyzwitterionhasanisoelectric
point(pI).TheisoelectricpointisthepHatwhichazwitterionisuncharged.
Aminoacid pI
Glycine 5.97
Tyrosine 5.66
Histidine 7.59
Lysine 9.74
Asparticacid 3.65
Classificationofaminoacids-
Theaminoacidshavebeenclassifiedonthebasisofthepolarityoftheirsidechains(Rgroup):
1.NonpolarAminoAcids-TheRgroupsinthisclassofaminoacidsarenonpolarand
hydrophobicwhichmaybealiphaticoraromatic.AminoacidswithnonpolaraliphaticRgroup
arealanine,valine,leucine,isoleucineandmethionine.Thenonpolarsidechainsofthese
aminoacidsstabilizetheproteinstructurethroughthehydrophobiceffect.Glycineisalsointhis
groupbutbecauseofsuchashortRgroupprovidesnorealhydrophobiceffect.Prolineisalso
anonpolaraminoacidwhichhasanaliphaticsidechainwithadistinctivecyclicstructurewitha
secondaryamino(imino)group.AminoacidswitharomaticRgroupsarePhenylalanine,
tyrosine,andtryptophanwhichalsostabilizeproteinmoleculesthroughhydrophobiceffect.
2.Polar,unchargedaminoacids-TheRgroupsoftheseaminoacidsaremoresolubleinwater,
(i.e.hydrophilic),thanthoseofthenonpolaraminoacids.Serine,threonine,cysteine,
asparagine,andglutaminearepolar,unchangedaminoacids.

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3.Acidicaminoacids(negativelychargedRgroups)-ThetwoaminoacidshavingRgroups
withanetnegativechargeatpH7.0areasparticacidandglutamicacid(bothhave-COOH
groupintheirsidechainRgroup).
4.Basicaminoacids(positivelychargedRgroups)-Theseaminoacidshavepositivechargein
theirsidechainRgroupandhencehavepositivechargeatpH7.0.Lysine,arginineand
histidinearetheexamples.
Thecommonaminoacidsofproteinshavebeenassignedthree-letterabbreviationsand
one-lettersymbols:
Histidine -His(H) Alanine -Ala(A)
Isoleucine-Ile(I) Arginine -Arg(R)
Leucine -Leu(L) Asparticacid-Asp(D)
Lysine -Lys(K) Cysteine -Cys(C)
Methionine-Met(M) Glutamicacid-Glu(E)
Phenylalanine-Phe(F) Glutamine-Gln(Q)
Threonine -Thr(T) Glycine -Gly(G)
Tryptophan-Trp(W) Proline -Pro(P)
Valine -Val(V) Serine -Ser(S)
Tyrosine -Tyr(Y) Asparagine-Asn(N)
Essentialaminoacids-Essentialaminoacidsarethoseaminoacidswhichcannotbe
synthesizedbyourbody.Asaresult,theymustcomefromourfood.The9essentialamino
acidsare-histidine,isoleucine,leucine,lysine,methionine,phenylalanine,threonine,
tryptophan,andvaline.Inaddition,arginineisconsideredasasemiessentialoraconditionally
essentialaminoacidbecauseitsendogenoussynthesismaynotbesufficienttomeetmetabolic
demandsinpreterminfantsandsomecasesofcriticalillness.PVTTIMHaLLisacommonly
useddevicetoremembertheseaminoacidsasitincludesthefirstletterofalltheessential
aminoacids.Acompleteproteinoradequateprotein,bydefinition,containsalltheessential
aminoacids.Completeproteinsusuallyderivefromanimal-basedsourcesofnutrition,except
forsoy(soybeansproteins).
PeptidesandProteins-Twoaminoacidmoleculescanbecovalentlyjoinedthrougha
substitutedamidelinkage,termedaspeptidebond.Suchalinkageisformedbyremovalofthe
elementsofwater(dehydration)fromtheα-carboxylgroupofoneaminoacidandtheα-amino
groupofanotherinacondensationreaction.Whenapeptidebondisformedbetweentwo
aminoacidstheresultantcompoundisdipeptide.Similarly,threeaminoacidscanbejoinedby
twopeptidebondstoformatripeptide;fouraminoacidscanbelinkedtoformatetrapeptide,
fivetoformapentapeptide,andsoforth.Whenafewaminoacidsarejoinedinthisfashion,the
structureiscalledanoligopeptide.Whenmanyaminoacidsarejoined,theproductiscalleda
polypeptideandthousandsofaminoacidslinktogethertoformproteins.Proteinsgenerally
havemolecularweightmorethan10000.Inapeptide,theaminoacidresidueattheendwitha
freeα-aminogroupistheamino-terminal(orN-terminal)residue;theresidueattheotherend,
whichhasafreecarboxylgroup,isthecarboxyl-terminal(C-terminal)residue.

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Whenanaminoacidsequenceofapeptide,polypeptide,orproteinisdisplayed,the
amino-terminalendisplacedontheleft,thecarboxyl-terminalendontheright.Thesequenceis
readlefttoright,beginningwiththeamino-terminalend.Example:Ifatripeptideconsistsof
glycine,histidineandphenylalanineandamino-terminalaminoacidisglycinewhilethe
carboxyl-terminalaminoacidisphenylalaninethenthistripeptideiswrittenas:glycyl-histidyl-
phenylalanineandinabbreviatedformasGly-His-Phe.
Threeglobalclassesofproteins-
1.Fibrousproteins-haverelativelysimple,regularlinearstructures.Theseproteinsoftenserve
structuralrolesincells.Typically,theyareinsolubleinwaterorindilutesaltsolutions.Examples
-keratins(hair),collagens(connectivetissues),myosins(muscles),andelastins(ligamentsand
arterialwalls).
2.Globularproteins-areroughlysphericalinshape.Thepolypeptidechainiscompactlyfolded
sothathydrophobicaminoacidsidechainsareintheinteriorofthemoleculeandthe
hydrophilicsidechainsareontheoutsideexposedtothesolvent.Examples-Hemoglobin,
myoglobin,albumin.
3.Membraneproteins-arefoundinassociationwiththevariousmembranesystemsofcells.As
such,membraneproteinsareinsolubleinaqueoussolutionsbutcanbesolubilizedinsolutions
ofdetergents.Thethreemaintypesofmembraneproteinsare-Integralmembraneproteins,
peripheralmembraneproteinsandlipid-anchoredproteins.Examples-histocompatibility
antigens,glycophorin,membraneimmunoglobulin,glycosyltransferasesetc.
Thefourlevelsofproteinstructure-
Primarystructure-givesthedescriptionofallcovalentbonds(mainlypeptidebondsand
disulfidebonds)andthelinearsequenceofaminoacidsinthepolypeptidechainofprotein.
Secondarystructure-describescertainpatternsoffoldinginthepolypeptidechaindueto
hydrogenbondingbetweenaminogroupsandcarboxylgroupsinneighboringregionsofthe
peptidechain.Twotypesofsecondarystructuresare:α–helixandβ–pleatedsheetstructures.
Theα–helixresultsfromtwistingofthepolypeptidechaininaright-handedscrewpattern.The
side-chainRgroupsoftheaminoacidinanα-helixextendtotheoutside.Hydrogenbondsform
betweentheoxygenofeachC=ObondinthestrandandthehydrogenofeachN-Hgroupfour
aminoacidsbelowitinthehelix.Thehydrogenbondsmakethisstructureespeciallystable.
Theβ-sheetconformationconsistsofpairsofstrands(polypeptide)lyingside-by-side.The
carbonyloxygensinonestrandbondswiththeaminohydrogensoftheadjacentstrand.Thetwo
strandscanbeeitherparallelorantiparalleldependingonwhetherthestranddirections
(N-terminustoC-terminus)arethesameoropposite.Theantiparallelβ-sheetismorestable
duetothemorewell-alignedhydrogenbonds.
Tertiarystructure-describestheoverallthree-dimensionalshapeofaproteinmolecule.This
resultsduetotwisting,foldingandcompactpackingofthepolypeptidechainresultingina

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globularthreedimensionalshape.Thisbendingandfoldinghelpstheproteintoachieve
maximumstabilityorlowestenergystate.Themainbondsandforcesresponsibleforthisthree
dimensionalglobularstructurearehydrogenbonds,hydrophobicinteractions,electrostatic
forces,vanderWaalsdispersionforcesanddisulphidebonds.
Quaternarystructure-Thecoalitionoftertiarystructurei.e.associationoftwoormoreindividual
proteinunits,eachwithitsowntertiarystructure,resultsinafurtherstablequaternarystructure.
Thefinalshapeoftheproteincomplexisonceagainstabilizedbyvariousinteractions,including
hydrogen-bonding,disulfide-bridgesandsaltbridges.
Testsofproteins/aminoacids-Therearesixtestsforthedetectionoffunctionalgroupsin
aminoacidsandproteins.Thesixtestsare:(1)NinhydrinTest(2)BiuretTest(3)Xanthoproteic
Test(4)Millon’sTest(5)Hopkins-ColeTestand(6)NitroprussideTest.
Ninhydrintest-Thealphaaminogroupofproteinsreactwithninhydrintogiveacoloured
complexfromdeepbluetovioletpink.However,inthecaseofiminoacidlikeprolineand
hydroxyproline,adifferentproducthavingabrightyellowcolorisformed.Asparagine,whichhas
afreeamidegroup,reactstogiveabrowncoloredproduct.
Biurettest-Alkalinecoppersulphatereactswithcompoundscontainingtwoormorepeptide
bondstogiveavioletorpinkishcolouredproductwhichisduetoformationofcoordination
complexofcupricionswithunsharedelectronpairsofpeptidenitrogenandoxygenofwater.

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XanthoproteicTest-Aminoacidscontaininganaromaticnucleus(e.g.tyrosineandtryptophan)
formyellownitroderivativesonheatingwithHNO3.Thesaltsofthesederivatives(byadditionof
alkali)areorangeincolor.Proteinscontainingtheseaminoacids(havingaromaticring)givea
positiveresponsetothistest.
Millon’sTest-AminoacidsorcompoundscontaininghydroxybenzeneradicalreactwithMillon’s
regentswhichconsistofmercurousandmercuricnitratescontainingHNO3,toformared
complex.Thusthistestisspecificfortyrosine.
Hopkins-ColeTest-Theindolegroupoftryptophanreactswithglyoxylicacidinthepresenceof
conc.H2SO4togiveapurplecolor.Glyoxylicacidispreparedbyreducingoxalicacidwith
magnesiumpowderorsodiumamalgam.Glacialacetic,whichhasbeenexposedtothe
sunlight,alsocontainsglyoxylicacidandcanthusbeusedforthistest.
Indolegroup Tryptophan
NitroprussideTest-Thenitroprussidetestisspecificforcysteine,theonlyaminoacidcontaining
afreesulfhydrylgroup(—SH).Thegroupreactswithnitroprussideinalkalinesolutiontoyielda
redcomplex.

7. 7
Methodforserumtotalproteinestimation-
Biuretmethod-Itisthemostcommonmethodforserumtotalproteinestimationwhichisbased
ontheprinciplethatserumproteinreactswithcupricioninanalkalinemediumtoproducea
violetcoloredcomplex.Theintensityofthecolor,whichhasmaximumabsorptionat540nm,is
proportionaltotheproteinconcentration.Theconcentrationofproteininserumiscalculatedby
comparingwiththeabsorbanceofproteinstandard.
Referenceintervalforserumtotalproteins-Thereferencerangeforserumtotalproteinis
typically60-80g/L.(6.0-8.0g/dl),butthismayvarydependingonthemethodofanalysis.
Methodforserumalbuminestimation-
Albuminisgenerallymeasuredbyadye-bindingtechniquethatutilizestheabilityofalbuminto
formastablecomplexwithbromocresolgreen(BCG)dye.ThecolouredBCG-albumincomplex
absorbslightat600-640nmandthecolourintensityisproportionaltoalbuminconcentration.
Thereferencevalueforserumalbuministypically3.5-5.5g/dlbutmayvary.
SerumTotalglobulinfraction=serumtotalprotein-serumalbumin
ENZYMES
Enzymesareaspecializedclassofproteins(ribozymesaretheexceptionwhichareRNA
molecules)whichactasbiocatalystsinthemetabolicreactionstospeeduptherateofaspecific
chemicalreaction.Theenzymeisnotdestroyedduringthereactionandisusedoverandover.
Thoughmanyenzymemoleculesarethetruecatalystbythemselves,someenzymesrequire
thepresenceofadditionalmoleculesforthefullexpressionoftheircatalyticfunction.
Someimportanttermsrelatedtoenzymestructureandfunction
Apoenzyme-istheenzymaticallyinactiveproteinpartofanenzyme,whichrequiresacofactor
foritsactivity.
Cofactor-isthenonproteinpartofanenzymewhichisrequiredforenzymeactivity.e.g.Mg2+,
Zn++,NAD.
Holoenzyme-Thecombinationofanapoenzymeandthecofactoriscalledholoenzymeandis
acomplete,functionalenzyme,whichiscatalyticallyactive.
Activator-Themetalioncofactorsarecalledactivators,suchasCu++,K+,Mg++etc.
Coenzyme-Thenonproteinorganiccofactormoleculeiscalledcoenzyme,suchasvitaminsof
Bgroup.
Prostheticgroup-Thetightlyboundcofactoriscalledprostheticgroup,suchasthiamine
pyrophosphateinpyruvatedehydrogenaseenzyme,biotininpyruvatecarboxylase,flavin
adeninedinucleotide(FAD)insuccinatedehydrogenase.
Substrate-isthechemicalsubstance,thetransformationofwhichiscatalyzedbyanenzyme.

8. 8
Activesite-Thepartofanenzymewherealltheeventsofthecatalyticprocessoccuriscalled
itsactivesite.
Functionofenzymes
Enzymesspeedup(catalyze)chemicalreactions.Itmeansthatenzymescanmakeachemical
reactionmanytimesfasterthanitwouldhavebeenwithoutit.
Asubstratebindstotheactivesiteofanenzymeandformsanenzyme-substratecomplex
whichisthenconvertedintoproducts.Oncetheproductsleavetheactivesite,theenzymeis
readytoattachtoanewsubstrateandrepeattheprocess.
Enzymeactivity
Thequantityorconcentrationofanenzymeisexpressedintermsofactivityinenzymeunits.
Anenzymeunit(activityasUorIU)istheamountofenzymethatwillcatalysethe
transformationof1μmolofsubstrateperminintoproductunderspecifiedconditionsofpHand
temperature.TheSIunitofenzymeactivityiskatal.Onekatalistheenzymeactivitythat
transformsonemoleofsubstratepersecondintoproductunderspecifiedassayconditions.
1U=16.67nkat(nanokatal)
Thespecificactivityofanenzymeisexpressedasthenumberofunitspermilligramofprotein.
TherateofabiochemicalreactionatagiventemperatureandpHdependsontheenzyme
concentrationandthesubstrateconcentration.Providedthesubstrateconcentrationremainsin
excess,theinitialrateisdirectlyproportionaltotheenzymeconcentration.
Isoenzymes-arethedifferentformsofanenzymecatalysingthesamereactionbutdifferingin
physico-chemicalpropertiessuchasaminoacidsequence,differentcombinationofsubunits,
heatstability,electrophoreticmobilityandsensitivitytoinhibitionbyexcessofsubstrate.These
variantsaregeneticallydetermined.Theseisoenzymesalsodifferintheirkineticandregulatory
propertiesandtheirdistributionintissueswhichisattributedtothemetabolicrequirementsofa
particulartissue.Thesearenumberedbasedontheirelectrophoreticmobilitytowardsanode.
Example:Lactatedehydrogenase(LDH)hasfiveisoenzymeswithLDH-5havingthelowest
mobilitytowardsanodeandLDH-1havingthehighestmobility.LDH-1ispresentinhighest

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concentrationinheartwhileLDH-5ispresentinhighestconcentrationinskeletalmusclesand
liver.
IsoenzymeCompositionPresentmainlyin Elevatedin
LD1 HHHH myocardium,RBCs myocardialinfarction
LD2 HHHM myocardium,RBCs
LD3 HHMM lungs,skeletalmuscles
LD4 HMMM kidneys,skeletalmuscles
LD5 MMMM liver,skeletalmuscles skeletalmusclesandliverdisease
—----------------------------------------------------------------------------------------------------------------------------
Likewise,enzymecreatinekinase(CK)hasthreeisoenzymes:
IsoenzymeCompositionPresentmainlyin Elevatedin
CK1 BB Brain CNSdisease
CK2 MB Myocardium AMI
CK3 MM Skeletalmuscles muscleinjury
Biochemicalmarkersofmyocardialinjury-
Myocardialischaemiaresultsfromthereductionofcoronaryflowtosuchanextentthatsupply
ofoxygentothemyocardiumdoesnotmeettheoxygendemandofmyocardialtissue.When
thisischaemiaisprolongedandirreversiblethenmyocardialcelldeathandnecrosisoccurs
whichisdefinedasmyocardialinfarction(MI).ThediagnosisofMIisbasedonclinical
symptoms,electrocardiographic(ECG)changesandcharacteristicpatternofchangesinsome
serumenzymessuchascreatinekinase(CK),creatinekinaseisoenzymeMB(CKMB),lactate
dehydrogenaseisoenzyme1(LD1)andcardiacspecificproteinsliketroponins.Sincetheclinical
symptomsarenotveryreliable,ECGisthemostwidelyusedmethodofthediagnosisof
myocardialinfarction.ButmanytimesECGshowsinconclusivepattern.Insuchasituationthe
importanceofserumbiochemicalmarkersofmyocardialinjuryarisestoconfirmthediagnosisof
myocardialinjury.
Criteriaforatruebiochemicalmarkerof
myocardialinjury:
1.Itshouldbemyocardialtissuespecificanditsconcentrationinthemyocardiumshouldbe
highbutshouldbeabsentinnon-myocardialtissues.
2.Itshouldbedetectableinbloodsoonafterthemyocardialinjuryi.e.thesensitivityshouldbe
high.
3.Itshouldremainelevatedinbloodforseveraldaysoftheonsetofdamagesothatitcanbe
detectedinpatientscomingtothehospitalquitelateaftermyocardialinfarction.
4.Itcouldbeassayedbysimpleandquickmethodi.e.theturn-aroundtime(TAT)shouldbelow
becausethefirstfewhoursofmyocardialinfarctionarecrucialformedicalintervention.
5.Itshouldgiveinformationregardingtheseverityoftheinfarctandtheprognosisofthe
disease.
6.ItshouldalsoshowtheresultofreperfusiontherapyinAMI.

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Thetablebelowdescribesthemarkersandtheircharacteristicsusedinthediagnosisof
myocardialinjury:
Enzyme/biomarker source onsetpeakatduration
SerumGOT myocardium,skeletalmuscles,liver3-8hrs24hrs3-6days
SerumLDH(total) myocardium,skeletalmuscles,liver6-12hrs48hrs4-14days
(andalmostallcellsofthebody)
SerumLDH1 mainlymyocardium,RBCs 6-12hrs48hrs4-14days
SerumCPK/CK(total) myocardium,skeletalmuscles <6hrs 24hrs2-3days
SerumCK-MB mainlymyocardium 3-5hrs16-20hrs2-3days
SerumcardiacTroponinTmyocardium 3-4hrs24-48hrs4-14days
SerumcardiacTroponinImyocardium 3-4hrs24-48hrs4-10days
SerumMyoglobin myocardium,skeletonmuscles 2-3hrs6-12hrs24-36hrs
Someofthesemarkerslikeaspartateaminotransferase,creatinekinase,lactatedehydrogenase
etc.havelosttheirutilityduetolessspecificityandlimitedsensitivity.Amongthecurrently
prevalentmarkersthetroponinsarepredominantlyusedforthediagnosisofmyocardialinjury
duetoitshighsensitivityspecificity,efficiencyandlowturnaroundtime.That'swhycardiac
troponinsareconsideredasthediagnostic‘goldstandard’formyocardialinjury.Thecombined
useofmyoglobinandcardiactroponinshasincreasedtheaccuracyofthediagnosisofacute
coronarysyndrome(ACS)andtherebyreducedthehospitalstayandexpensesofthepatients.
Someotherpromisingmarkersofearlydiagnosisofmyocardialdamageare-heartfattyacid
bindingprotein(hFABP),glycogenphosphorylaseBB,myoglobin/carbonicanhydraseIIIratio,
copeptinandirisin,butsearchforthemostidealmarkerisstillon.
INHINGLISH
प्रोटीन्स(proteins)क्याहैं-प्रोटीन्सहमारेशरीरकीसभीकोशिकाओंमेंबड़ीमात्राऔरविभिन्नप्रकारमेंपायी
जातीहैंIयेअमीनोएसिड्सकेpolymerहोतेहैंजो20अमीनोएसिड्सकेभिन्न-भिन्नcombinationsऔर
सीक्वेन्सेसकेबनेहोतेहैंIप्रत्येकअमीनोएसिडअपनेपड़ोसीअमीनोएसिडसेएकविशिष्टप्रकारकेcovalent
bond,जिसे'peptidebond'कहतेहैं,द्वाराजुड़ाहोताहैI
Someimportantfunctionsofproteinsinourbody:
●वोproteinsजोcatalystsकाकामकरतीहैंउन्हेंenzymesकहतेहैंऔरयेenzymesविभिन्न
biochemicalreactionsकीरफ़्तारबढ़ातेहैंI
●प्रोटीन्स,cellmembranesकेसंरचनात्मकघटक(structuralcomponents)होतेहैंI

11. 11
●कुछproteinstransportprocessesमेंमददकरतेहैं,जैसे-lipoproteinsद्वाराlipidsकाtransport
औरहीमोग्लोबिनद्वाराoxygenकाtransport
●कुछप्रोटीन्सशरीरकीप्रतिरक्षाप्रणालीमेंमददकरतेहैं,जैसे-antibodies
●कुछप्रोटीन्सchemicalmessengersकोपहचाननेकेलिएreceptorकाकामकरतीहैंI
●कुछchemicalmessengersproteinsहोतेहैं,जैसे-hormones
●Proteinsशरीरकोstructuralsupportऔरmovementभीप्रदानकरतेहैं,जैसे-connective
tissuesऔरmusclesकेproteinfibres.
Aminoacids-
प्रोटीन्समेंसाधारणतया20भिन्न-भिन्नप्रकारकेaminoacidsपायेजातेहैंIअमीनोएसिडAsparagineकी
खोजसबसेपहलेहुईथीऔरसबसेअन्तमेंThreonineकीI
अमीनोएसिड्सकीसामान्यसंरचनात्मकविशेषतायें-अमीनोएसिड्सorganiccompoundsहैंजिनमेंएक
acidiccarboxylgroup(-COOH)औरएकbasicaminogroup(-NH2)होताहैऔरयेदोनोंgroupsएकही
carbonatom(theαcarbon)जोcarboxylcarbonकेबगलमेंहोताहै,सेजुड़ेहोतेहैंIइसकेअतिरिक्त,
इनमेंएकsidechainयाRgroupहोताहैजोप्रत्येकअमीनोएसिडकेलिएविशिष्टहोताहैऔरयहRgroup
structure,size,औरelectricchargeमेंभिन्न-भिन्नहोताहैतथायहअमीनोएसिड्सकीपानीमें
घुलनशीलताकोप्रभावितकरताहैI
Theformulaofageneralaminoacid-isRCH(NH2)COOH.
Glycineकोछोड़करसभीअमीनोएसिड्सकेदोenantiomers(D-andL-forms,mirrorimageofeach
other)होतेहैंIऐसाइसलिएक्योंकिglycineकेअतिरिक्तसभीसामान्यअमीनोएसिड्समेंएकαcarbon
होताहैजिससेचारअलग-अलगgroupsजुड़ेहोतेहैं:एकcarboxylgroup,एकaminogroup,एकR
group,औरएकhydrogenatom(जबकिglycineमेंRgroupएकअन्यhydrogenहोताहै)Iइन
stereoisomersकाविन्यास(configuration)D-औरL-glyceraldehydeकेविन्याससेसम्बंधितहैI
L-Aminoacidsमेंα-aminogroupबायींतरफहोताहैऔरD-aminoacidsमेंα-aminogroupदाहिनीतरफ
होताहैI
Aminoacidswater(neutralpH)मेंdipolarions(zwitterions)केरूपमेंरहतेहैंजोacidयाbaseकीतरह
कार्यकरतेहैंIDipolarformमेंaminogroupprotonated(NH3+)होताहैऔरcarboxylgroup
deprotonated(COO–)होताहैIइसतरहकादोहरास्वभाव(acid-base)रखनेवालेपदार्थamphotericहोते
हैंऔरइन्हेंampholyteकहतेहैंIअमीनोएसिड्सकीionizationstatesolutionकेpHकेअनुसारबदल
सकतीहैIpHmoleculeकेchargeकोप्रोटोन(H+)द्वाराबदलसकताहैक्योंकिअमीनोacidकाamino
groupएकबहुतप्रभावीprotonacceptorहै,इसलिएअमीनोग्रुपकोbasicमानाजाताहैIइसीतरह,
carboxylgroupएकप्रभावीprotondonorहोनेकेकारणacidicमानाजाताहैIप्रत्येकzwitterionकाएक
isoelectricpoint(pI)होताहै(isoelectricpointवोpHहोताहैजिसपरzwitterionबिनाकिसीcharge
(uncharged)काहोताहै)I

12. 12
Aminoacid pI
Glycine 5.97
Tyrosine 5.66
Histidine 7.59
Lysine 9.74
Asparticacid 3.65
अमीनोएसिड्सकावर्गीकरण-
Aminoacidsकोउनकीsidechains(Rgroup)कीpolarityकेआधारपरवर्गीकृतकियागयाहै:
1.NonpolarAminoAcids-इसgroupकेअमीनोएसिड्सकेRgroupsnonpolarऔरhydrophobicहोते
हैंऔरयेaliphaticयाaromaticहोसकतेहैंIउदाहरण-nonpolaraliphaticRgroupsवालेअमीनोएसिड्स
-alanine,valine,leucine,isoleucineऔरmethionineIइनकीnonpolarsidechainsprotein
structureकोhydrophobiceffectद्वाराstabilizeकरतीहैIGlycineभीइसीgroupमेंहैकिन्तुRgroup
(H)केबहुतछोटाहोनेकेकारणhydrophobiceffectनहींहोपाताIProlineभीएकnonpolaraminoacid
हैजिसकीaliphaticsidechainकाएकविशेषcyclicstructureहोताहैजिसमेंएकsecondaryamino
(imino)groupभीहोताहैIAromaticRgroupssidechainवालेअमीनोएसिड्स-Phenylalanine,
tyrosine,औरtryptophanभीhydrophobiceffectद्वाराप्रोटीनकेstabilizationमेंयोगदानदेतेहैंI
2.Polar,unchargedaminoacids-Serine,threonine,cysteine,asparagine,औरglutamine
polar,unchangedaminoacidsहैंIइनकेsidechainमेंएकhydroxyl,amideयाएकsulfhydrylgroup
होताहै,जैसे-serine(hydroxylgroup),cysteine(sulfhydrylgroup)औरइनकाRgroupnonpolar
अमीनोएसिड्सकीतुलनामेंपानीमेंघुलनशील(यानिhydrophilic)होताहैI
3.Acidicaminoacids(NegativelyChargedRGroups)-दोaminoacidsजिनकेRgroupsपरpH
7.0परएकnegativechargeहोताहै,वोहैं-asparticacidऔरglutamicacid(दोनोंकेsidechainR
groupमें-COOHgroupहोताहै)I
4.Basicaminoacids(PositivelyChargedRGroups)-इनaminoacidsकेsidechainRgroupमें
positivechargeहोताहै,इसीलिएइनअमीनोएसिड्सपरpH7.0परpositivechargeहोताहैIउदाहरण-
Lysine,arginineऔरhistidine
प्रोटीन्सकेसामान्यअमीनोएसिड्सकोthree-letterabbreviationsऔरone-lettersymbolsसेदर्शातेहैं:
Histidine -His(H) Alanine -Ala(A)
Isoleucine-Ile(I) Arginine -Arg(R)
Leucine -Leu(L) Asparticacid-Asp(D)
Lysine -Lys(K) Cysteine -Cys(C)
Methionine-Met(M) Glutamicacid-Glu(E)
Phenylalanine-Phe(F) Glutamine-Gln(Q)
Threonine-Thr(T) Glycine -Gly(G)
Tryptophan-Trp(W) Proline -Pro(P)
Valine -Val(V) Serine -Ser(S)
Tyrosine -Tyr(Y) Asparagine-Asn(N)

13. 13
Essentialaminoacids-वोअमीनोएसिड्सजोहमारेशरीरमेंsynthesizeनहींहोपातेकिन्तुशरीरको
सुचारुरूपसेचलानेहेतुअतिआवश्यकहोतेहैंIइसलिएइनकोहमेंअपनेभोजनद्वाराप्राप्तकरनापड़ताहैIये
9essentialaminoacidsहैं-histidine,isoleucine,leucine,lysine,methionine,phenylalanine,
threonine,tryptophan,andvaline.इसकेअतिरिक्त,arginineकोएकsemiessentialयाएक
conditionallyessentialaminoacidकहाजाताहैक्योंकिpreterminfantsऔरकुछcriticalillnessमें
हमारेशरीरमेंइसकीज़रूरतकेअनुरूपsynthesisनहींहोपातीहै,इसलिएइसकीअतिरिक्तमात्राहमेंdietमें
शामिलकरनीपड़तीहैIessentialaminoacidsकेनामयादरखनेहेतु"PVTTIMHaLL"काइस्तेमालकरते
हैंजोइनessentialaminoacidsकेपहलेletterसेबनाहैIजिनproteinsमेंसभीessentialaminoacids
उपस्थितहोतेहैं,उन्हेंcompleteproteinsयाadequateproteinsकहतेहैंICompleteproteinsसामान्य
तौरपरपशुआधारितस्रोतसेप्राप्तहोतीहैंIहालांकि,शाकाहारीस्रोतमेंsoybeansहैजिससेहमेंcomplete
proteinsप्राप्तहोतीहैंI
PeptidesऔरProteins-दोअमीनोएसिडmoleculesएकamidelinkage,जिसेpeptidebondकहतेहैं,
द्वाराजुड़सकतेहैंIऐसाlinkageएकअमीनोएसिडकेα-carboxylgroupऔरदूसरेअमीनोएसिडके
α-aminogroupसेcondensationreactionद्वाराएकwatermoleculeकोहटानेसे(dehydration)बनता
हैIजबदोअमीनोएसिड्सकेबीचएकpeptidebondबनताहैतोइसकेपरिणामस्वरुपबननेवाले
compoundकोdipeptideकहतेहैंIइसीप्रकार,तीनaminoacidsकोदोpeptidebondsद्वाराजोड़नेसे
tripeptide;चारaminoacidsजुड़करएकtetrapeptide,पांचअमीनोएसिड्सकोजोड़नेसेएक
pentapeptideबनताहैIइसतरहदोसेबीसअमीनोएसिड्ससेबनेcompoundsकोoligopeptideया
peptide(oligo-"afew")कहतेहैंI20सेभीअधिकaminoacidsकेजुड़नेसेबनेproductकोpolypeptide
औरहज़ारोंaminoacidsसेबनेproductsकोproteinsकहतेहैंIProteinsकाmolecularweight
साधारणतया10000सेअधिकहोताहैIएकpeptideकेएकछोरपरaminoacidresidueजिसमेंएकfree
α-aminogroupहोताहै,amino-terminal(orN-terminal)residueकहलाताहैऔरदूसरेendपरजोamino
acidresidueजिसकाcarboxylgroupfreeहोताहै,वोcarboxyl-terminal(C-terminal)residueकहलाता
हैI
जबएकpeptide,polypeptideयाproteinकेaminoacidsequenceकोदर्शातेहैंतोamino-terminalend
कोबायींतरफऔरcarboxyl-terminalendकोदाहिनीतरफदर्शातेहैंIइसतरहaminoacidsकेsequence
कोamino-terminalendसेबाएंसेदाएंपढ़तेहैंIउदाहरण:यदिकोईpeptideजिसमेंतीनaminoacids-
glycine,histidineऔरphenylalanineहैंऔरamino-terminalaminoacidglycineहैऔर
carboxy-terminalaminoacidहैphenylalanineतोइसtripeptideतोलिखेंगे:glycyl-histidyl-
phenylalanineऔरabbreviationमेंलिखेंगे:Gly-His-Phe
Threeglobalclassesofproteins-
1.Fibrousproteins-इनप्रोटीन्सकाstructureअपेक्षाकृतsimpleऔरregularlinearहोताहैIयेप्रोटीन्स
अक्सरcellsमेंसंरचनात्मकभूमिकानिभातीहैंIआमतौरपरयेwaterऔरdilutesaltsolutionsमें
अघुलनशीलहोतीहैंIउदाहरण-keratins(hair),collagens(connectivetissues),myosins(muscles)
औरelastins(ligamentsandarterialwalls).

14. 14
2.Globularproteins-येप्रोटीन्सआमतौरपरएकगेंदकेआकारकीहोतीहैंIइनकीpolypeptidechain
compactlyfoldedहोतीहैंजिससेhydrophobicaminoacidsidechainsproteinmoleculeकेआंतरिक
भागमेंहोजाएंऔरhydrophilicsidechainsबाहरकीतरफsolventकीओरअनावृत(exposed)होंI
उदाहरण-Hemoglobin,myoglobin,albumin.
3.Membraneproteins-येproteinscellsकेविभिन्नmembranesystemsसेसंयुक्तरूपमेंपायीजातीहैं
Iवैसेतोmembraneproteinsजलीयविलयनमेंअघुलनशीलहोतीहैंकिन्तुइन्हेंdetergentsकेविलयनमें
घोलाजासकताहैIतीनमुख्यप्रकारकीmembraneproteinsहैं-Integralmembraneproteins,
peripheralmembraneproteinsandlipid-anchoredproteins.उदाहरण-histocompatibilityantigens,
glycophorin,membraneimmunoglobulin,glycosyltransferases.
Thefourlevelsofproteinstructure-
1.Primarystructure-सेproteinमेंमौजूदसभीcovalentbonds(mainlypeptidebondsanddisulfide
bonds)काविवरणऔरproteinsकीpolypeptidechainsकेअमीनोacidsकेlinearsequenceकापता
चलताहैI
2.Secondarystructure-मेंpolypeptidechainमेंउसकेनज़दीकीहिस्सोंकेaminogroupsऔरcarboxyl
groupsकेबीचhydrogenbondingकेफलस्वरुपहुईfoldingकेpatternकापताचलताहैIदोप्रकारके
secondarystructuresहैं:α–helixऔरβ–pleatedsheetstructures.Theα–helix,polypeptidechain
केright-handedscrewpatternमेंtwistingसेबनताहैIइसमेंaminoacidsकेside-chainRgroups
बाहरकीतरफविस्तारित(extended)होतेहैंIstrandकेप्रत्येकC=Obondकेoxygenऔरhelixमेंप्रत्येक
चारaminoacidsनीचेN-HकेhydrogenकेबीचhydrogenbondsबनतेहैंIयेHydrogenbondsइस
structureकोविशेषरूपसेस्थिरबनातेहैंI
β-sheetconformationमेंpolypeptidestrandsकाजोड़ासाथ-साथहोताहैIएकstrandकेcarbonyl
oxygensजोड़ेकेstrandकेaminohydrogensकेसाथbondsबनातेहैंIदोनोंstrandsएकदूसरेकेparallel
याantiparallelहोसकतेहैंजोइसपरनिर्भरकरताहैकिदोनोंstrandsकीदिशा(N-terminusto
C-terminus)एकहीहैयाएकदूसरेकीउल्टी(antiparallel)IAntiparallelβ-sheet,well-aligned
hydrogenbondsकेकारण,अधिकस्थिरहोतीहैI
3.Tertiarystructure-proteinmoleculeकेglobularthree-dimensionalshapeकाविवरणदेताहैजो
polypeptidechainकीtwisting,foldingऔरcompactpackingकेफलस्वरुपबनताहैऔरइससेprotein
कोअधिकतमस्थिरताऔरन्यूनतमenergyअवस्थाप्राप्तकरनेमेंमददमिलतीहैIइसthreedimensional
globularstructureकेलिएमुख्यरूपसेज़िम्मेदारbondsऔरforcesहैं-hydrogenbonds,hydrophobic
interactions,electrostaticforces,vanderWaalsdispersionforcesऔरdisulphidebonds
4.Quaternarystructure-बनताहैदोयाअधिकअलग-अलगproteinunits(अपने-अपनेtertiary
structureमें)केगठबंधनसेऔरयहtertiarystructureसेऔरअधिकस्थिरहोताहैIप्रोटीनcomplexका
finalshapeविभिन्नinteractions,जिनमेंhydrogen-bonding,disulfide-bridgesऔरsaltbridges
शामिलहैं,द्वाराऔरस्थिरताप्राप्तकरताहैI

15. 15
Testsofproteins/aminoacids-Aminoacidsऔरproteinsकेfunctionalgroupsकीजाँचकेलिए
छहtestsकाउपयोगकरतेहैं:(1)NinhydrinTest(2)BiuretTest(3)XanthoproteicTest(4)Millon’s
Test(5)Hopkins-ColeTestand(6)NitroprussideTest.
Ninhydrintest-Proteinsकाalphaaminogroupninhydrinकेसाथreactकरकेएकcolouredcomplex
बनातीहैंजोdeepblueसेvioletpinkहोताहैIहालांकि,iminoacidजैसे-prolineऔरhydroxyproline,
brightyellowcolorदेतेहैंIइसीतरह,Asparagine,जिसमेंएकfreeamidegroupहोताहै,browncolored
productदेताहैl
Biurettest-Alkalinecoppersulphateदोयाअधिकpeptidebondsवालेcompoundsसेreactकरके
एकvioletयाpinkishcolouredcomplexबनाताहैI
XanthoproteicTest-वोaminoacidsजिनमेंएकaromaticnucleusहोताहैवोHNO3केसाथगर्मकरने
परyellownitroderivativesबनातेहैंIइनderivativesकेalkaliकेसाथreactकरनेपरबनेsaltorange
colourकेहोतेहैंIइसप्रकारaromaticringवालेअमीनोएसिड्स(जैसे-tyrosineऔरtryptophan)वाली
proteinsयहtestpositiveदेतीहैंI

16. 16
Millon’sTest-Aminoacidsयाcompoundsजिनमेंhydroxybenzeneradicalहोताहै,वेMillon’s
reagent(mercurous+mercuricnitrates+HNO3)केसाथएकredcolourकाcomplexबनातेहैंIयह
testtyrosineकेलिएspecificहोताहैक्योंकिइसमेंhydroxybenzeneradicalहोताहैI
Hopkins-ColeTest-Tryptophanaminoacidकाindolegroupconc.H2SO4कीउपस्थितिमें
glyoxylicacidसेreactकरकेएकpurplecolorकीringबनाताहैI
Tryptophan Indolegroup
NitroprussideTest-यहtestcysteine(aminoacidजिसमेंएकfreesulfhydryl,—SHgroupहोताहै)के
लिएspecificहोताहैI–SHgroupnitroprussideकेसाथalkalinesolutionमेंreactकरकेएकred
complexबनाताहैI
Methodforproteinestimation-
Biuretmethod-Serumtotalproteinestimationकायहसबसेसामान्यmethodहै,जिसकाआधार
(principle)यहहैकिserumproteinsalkalinemediumमेंcupricionsकेसाथएकvioletcolourका
complexबनातीहैंIइसcomplexकेcolourकीintensityकाmaximumabsorption540nmपरहोताहै
औरयहproteinconcentrationकासीधाअनुपातिकहोताहैISerumमेंproteinकाconcentrationएक
proteinstandardद्वारादिएcolourकीintensity(absorbance)सेतुलनाकरकेcalculateकरतेहैंI
Referenceintervalforserumtotalproteins-Thereferencerangeforserumtotalproteinis
typically60-80g/L(6.0-8.0g/dl),butthismayvarydependingonthemethodofanalysis.
Methodforserumalbuminestimation-

17. 17
Serumalbuminसामान्यतौरपरएकdye-bindingtechniqueद्वाराestimateकियाजाताहैजोइस
सिद्धांतपरआधारितहैकिalbuminbromocresolgreen(BCG)dyeकेसाथreactकरकेएकstable
complexबनाताहैIयहcolouredBCG-albumincomplex600-640nmपरmaximumabsorptionदेता
हैऔरइसकीcolourintensityalbuminconcentrationकेसीधाअनुपातिकहोतीहैISerumalbuminका
referenceintervalआमतौरपर3.5-5.5g/dlकिन्तुयहभिन्नभीहोसकताहैI
SerumTotalglobulinfraction=serumtotalprotein-serumalbumin
ENZYMES
Enzymesproteinsकाएकविशेषीकृत(specialized)वर्गहैं(ribozymesकोछोड़कर,जोRNAmolecules
हैं)जोmetabolicreactionsमेंbiocatalystsकाकामकरतेहैंऔरविशेषchemicalreactionsकीspeed
बढ़ातेहैंIchemicalreactionsकेदौरानenzymesनष्टनहींहोतेऔरबार-बारइस्तेमालहोतेहैंIयद्यपि
बहुतसेenzymemoleculesखुदहीtruecatalystहोतेहैंकिन्तुकुछenzymesकोपूर्णcatalyticfunction
हेतुकुछअन्यmoleculesकीआवश्यकताहोतीहैI
Someimportanttermsrelatedtoenzymestructureandfunction:
Apoenzyme-किसीenzymeकेenzymaticallyinactiveproteinpartकोapoenzymeकहतेहैंIइस
inactivepartकोactivateकरनेहेतुएकcofactorकीआवश्यकताहोतीहैI
Holoenzyme-Apoenzymeऔरcofactorकेसंयोजनसेholoenzymeबनताहैऔरitisthecomplete,
functionalenzyme,whichiscatalyticallyactive.
Cofactor-isthenonproteinpartofanenzymewhichisrequiredforenzymeactivity.e.g.Mg++,
Zn++,NAD
Activator-Themetalioncofactorsarecalledactivators,suchasCu++,K+,Mg++etc.
Coenzyme-Thenonproteinorganiccofactormoleculeiscalledcoenzyme,suchasvitaminsof
Bgroup.
Prostheticgroup-Thetightlyboundcofactoriscalledprostheticgroup,suchasthiamine
pyrophosphateinpyruvatedehydrogenaseenzyme,biotininpyruvatecarboxylase,flavin
adeninedinucleotide(FAD)insuccinatedehydrogenase.
Substrate-isthechemicalsubstance,thetransformationofwhichiscatalyzedbyanenzyme.
Activesite-Thepartofanenzymewherealltheeventsofthecatalyticprocessoccuriscalled
itsactivesite.
Functionofenzymes
Enzymesspeedup(catalyze)chemicalreactions.इसकामतलबहैकिenzymeschemicalreaction
कीगतिकोकईगुनाअधिकतीव्रकरसकतेहैं,बिनाenzymeकीउपस्थितिमेंreactionकीगतिकीतुलनामेंI
जबएकsubstrateenzymeकीactivesiteसेbindकरताहैतोएकenzyme-substratecomplex
बनताहैजोफिरproductsमेंपरिवर्तितहोताहैIजबproductsactivesiteकोछोड़तेहैंतोenzymeदूसरेनए
substratemoleculeकोbindकरनेकेलिएतैयारहोजाताहैऔरफिरproductsबननेकीप्रक्रियाकी
पुनरावृत्तिहोतीहैI

18. 18
Enzymeactivity
एकenzymeकीquantityयाconcentrationकोactivityकेरूपमेंenzymeunitsद्वारादर्शातेहैंIएक
enzymeunit(activityasUorIU)enzymeकीवोमात्राहैजो1मिनटमेंsubstrateके1μmolको
productमेंtransformationकोcatalyzeकरतीहै(underspecifiedconditionsofpHand
temperature).EnzymeactivityकीSIunitkatalहैIonekatalenzymeactivitysubstrateके1mole
को1सेकंडमेंproductमेंtransformकरतीहै(underspecifiedassayconditions)I
1U=16.67nkat(nanokatal)
Thespecificactivityofanenzymeisexpressedasthenumberofunitspermilligramofprotein.
TherateofabiochemicalreactionatagiventemperatureandpHdependsontheenzyme
concentrationandthesubstrateconcentration.Providedthesubstrateconcentrationremainsin
excess,theinitialrateisdirectlyproportionaltotheenzymeconcentration.
Isoenzymes-Isoenzymesकिसीenzymeकेविभिन्नरूपहोतेहैंजोsamereactionकोcatalyzeकरतेहैं
किन्तुउनकीphysico-chemicalpropertiesजैसे-aminoacidsequence,differentcombinationof
subunits,heatstability,electrophoreticmobilityandsensitivitytoinhibitionbyexcessof
substrateआदिभिन्नहोतीहैंIयेभिन्नरूप(variants)आनुवंशिकरूपसेनिर्धारितहोतेहैंIIsoenzymes
अपनीkineticऔरregulatorypropertiesएवंtissuesमेंउनकेdistributionमेंभीभिन्नहोतेहैंजिसकेलिए
विशिष्टtissueकीmetabolicrequirementsजिम्मेदारहोतीहैंIIsoenzymesकोउनकीanodeकीओर
electrophoreticmobilityकेआधारपरसंख्यांकितकियाजाताहैIउदाहरण:Lactatedehydrogenase
(LDH)केपाँचisoenzymesहोतेहैंजिनमेंLDH-5कीanodeकीतरफmobilityसबसेकमहोतीहैऔर
LDH-1कीसबसेअधिकILDH-1कीमात्राheartमेंसबसेअधिकहोतीहैजबकिLDH-5कीसबसेअधिक
मात्राskeletalmusclesऔरliverमेंहोतीहैI
IsoenzymeCompositionPresentmainlyin Elevatedin
LD1 HHHH myocardium,RBCs myocardialinfarction
LD2 HHHM myocardium,RBCs
LD3 HHMM lungs,skeletalmuscles
LD4 HMMM kidneys,skeletalmuscles
LD5 MMMM liver,skeletalmuscles skeletalmusclesandliverdisease
—----------------------------------------------------------------------------------------------------------------------------
इसीप्रकारcreatinekinase(CK)enzymeकेतीनisoenzymesहोतेहैं:
IsoenzymeCompositionPresentmainlyin Elevatedin
CK1 BB Brain CNSdisease
CK2 MB Myocardium AMI
CK3 MM Skeletalmuscles muscleinjury
Biochemicalmarkersofmyocardialinjury-coronary(कोरोनरी)artery(धमनी)मेंजबकिसी
कारणवशbloodकेप्रवाहमेंरुकावटहोतीहैतोmyocardium(heartकीmuscularlayer)को
आवश्यकतानुसारऑक्सीजननहींमिलपातीतोइसस्थितिकोmyocardialischaemiaकहतेहैंIजबयह
ischaemiaअधिकसमयकेलिएऔरअपरिवर्तनीयहोजाताहैतोmyocardialcellsकीdeathऔरnecrosis
(गलजाना)होनेलगतीहैऔरइसेmyocardialinfarction(रोधगलन,MI)यातीव्ररोधगलन(acute

19. 19
myocardialinfarction,AMI)कहतेहैंऔरजिसेआमतौरपरहृदयाघात(हार्टअटैक)यादिलकेदौरेकेरूपमें
जानाजाताहैIMIकीdiagnosisclinicalsymptoms,electrocardiographic(ECG)changesऔरserum
मेंउपस्थितbiochemicalmarkersजैसे-कुछenzymes(creatinekinase(CK),creatinekinase
isoenzymeMB(CKMB),lactatedehydrogenaseisoenzyme1,LD1)औरcardiacspecificproteins
जैसे-troponins,केपरिवर्तनकेविशिष्टपैटर्न(characteristicpatternofchanges)केआधारपरकीजातीहै
Iचूंकिclinicalsymptomsबहुतअधिकreliableनहींहोतेहैं,इसलिएmyocardialinfarctionकीdiagnosis
हेतुECGकाहीसबसेअधिकइस्तेमालहोताहैIकिन्तुबहुतबारECGसेभीMIकीdiagnosisसुनिश्चितनहीं
होपातीहै,औरतबऐसीपरिस्थितिमेंserumमेंउपस्थितmyocardialinjuryकेइनbiochemicalmarkers
कीमददसेMIकीdiagnosisकीजातीहैI
Myocardialinjuryकेएकअसलीbiochemicalmarkerकेमुख्यमानदंड(Maincriteriaforatrue
biochemicalmarkerofmyocardialinjury):
1.यहmarkermyocardialtissueकेलिएविशिष्ट(specific)होनाचाहिएऔरइसकाmyocardiumमें
concentrationउच्चहोनाचाहिएकिन्तुअन्यगैरmyocardialtissuesमेंअनुपस्थितहोनाचाहिएI
2.ब्लडमेंइसकास्तरmyocardialinjuryकेशीघ्रबादहीपताकरनेयोग्य(detectable)होनाचाहिएअर्थात
इसकीसंवेदनशीलता(sensitivity)अत्यधिकहोनीचाहिएI
3.ब्लडमेंइसकास्तरक्षतिकीशुरुआतकेबादकईदिनोंतकबढ़ारहनाचाहिएताकिजोमरीज़myocardial
infarctionकेबाददेरसेअस्पतालपहुँचेउनमेंभीइसकेस्तरकोdetectकियाजासकेI
4.Markerकीजाँचविधिसरलऔरत्वरित(quick)होनीचाहिएयानिइसकाप्रतिवर्तनकाल(turn-around
time,TAT)कमहोनाचाहिएक्योंकिmyocardialinfarctionहोनेकेबादकेपहलेकुछघंटेइलाजकेलिएबहुत
महत्वपूर्णहोतेहैंI
5.इसकेद्वारारोधगलितांश(infarct)कीगंभीरताऔररोगकाफलानुमानकाभीअनुमानलगायाजासकेI
6.इसकेद्वाराAMIहोनेपरकीगईreperfusiontherapyकेपरिणामकाभीपतालगनाचाहिएI
नीचेtableमेंmyocardialinjuryकीdiagnosisकेलिएउपयोगहोनेवालेmarkersऔरउनकीविशेषताएं
(characteristics)दीहुईहैं:
Enzyme/biomarker presentin onsetpeakduration
SerumLDH(total) myocardium,skeletalmuscles,liver6-12hrs48hrs4-14days
(andalmostallcellsofthebody)
SerumLDH1 mainlymyocardium,RBCs 6-12hrs48hrs4-14days
SerumCPK/CK(total) myocardium,skeletalmuscles <6hrs24hrs2-3days
SerumCK-MB mainlymyocardium 3-5hrs16-20hrs2-3days
SerumcardiacTroponinTmyocardium 3-4hrs24-48hrs4-14days
SerumcardiacTroponinImyocardium 3-4hrs24-48hrs4-10days
SerumMyoglobin myocardium,skeletonmuscles 2-3hrs6-12hrs24-36hrs

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इनमेंसेकुछmarkersजैसे-aspartateaminotransferase,creatinekinase,lactatedehydrogenase
आदिspecificityकेनहींहोनेऔरसिमितsensitivityकेकारणअपनीउपयोगिताखोचुकेहैंIवर्तमानमें
प्रचलितmarkersमेंtroponinsहीअपनीउन्नतsensitivityspecificity,efficiencyऔरकमturnaround
timeकेकारणसर्वाधिकउपयोगमेंहैंIयहाँतककिcardiactroponinsकोmyocardialinjuryकीdiagnosis
हेतुdiagnostic‘goldstandard’कहाजानेलगाहैIMyoglobinऔरcardiactroponinsकेसंयुक्तरूपसे
उपयोगनेacutecoronarysyndromeकीdiagnosisकीaccuracyकोऔरभीबढ़ादियाहैजिसकेकारण
मरीज़काअस्पतालमेंरहनाऔरखर्चेमेंभीकमीहोतीहैIMyocardialdamageकीअतिशीघ्रdiagnosisके
लिएकुछअन्यनएआशाजनक(promising)markersभीहैं,जैसे-heartfattyacidbindingprotein
(hFABP),glycogenphosphorylaseBB,myoglobin/carbonicanhydraseIIIratio,copeptinऔर
irisin,किन्तुmostidealmarkerकीखोजअबभीजारीहैI
Somepracticequestions
Q.1.Fillintheblanks:
(i)प्रोटीन्स______केpolymersहोतेहैंI
(ii)प्रोटीन्सकुल_____अमीनोएसिड्सकेभिन्न-भिन्नcombinationsऔरसीक्वेन्सेसकेबनेहोतेहैंI
(iii)प्रोटीन्समेंप्रत्येकअमीनोएसिडअपनेपड़ोसीअमीनोएसिडसेएकविशिष्टप्रकारकेbond,जिसे
_______bondकहतेहैं,द्वाराजुड़ाहोताहैI
(iv)वोproteinsजोcatalystsकाकामकरतीहैंउन्हें______कहतेहैंI
(v)प्रोटीन्स,cellmembranesके______घटक(components)होतेहैंI
(vi)_______द्वाराlipidsकाtransportऔर______द्वाराoxygenकाtransportहोताहैI
(vii)कुछप्रोटीन्सशरीरकीप्रतिरक्षाप्रणालीमेंमददकरतीहैं,उन्हें________कहतेहैंI
(viii)कुछproteinschemicalmessengersकाकामकरतीहैं,उन्हें_______कहतेहैंI
(ix)अमीनोएसिड्सorganiccompoundsहैंजिनमेंएक_____groupऔरएक_____groupहोताहैI
(x)_____कोछोड़करसभीअमीनोएसिड्सकेदोenantiomers(D-andL-forms)होतेहैंI
(xi)Aminoacidswaterमें________ionsकेरूपमेंरहतेहैंजोacidयाbaseकीतरहकार्यकरतेहैंI
(xii)वोpHजिसपरzwitterionबिनाकिसीchargeयानिunchargedकाहोताहै,उसpHको__________
pointकहतेहैंI
(xiii)वोअमीनोएसिड्सजोहमारेशरीरमेंsynthesizeनहींहोपातेकिन्तुशरीरकोसुचारुरूपसेचलानेहेतु
अतिआवश्यकहोतेहैं,उन्हें________aminoacidsकहतेहैंI
(xiv)जिनproteinsमेंसभीessentialaminoacidsउपस्थितहोतेहैं,उन्हें_______proteinsया______
proteinsकहतेहैंI
(xv)Completeproteinsसामान्यतौरपरपशुआधारितस्रोतसेप्राप्तहोतीहैंकिन्तु_______complete
proteinsकाएकशाकाहारीस्रोतहैI
(xvi)जबदोअमीनोएसिड्सकेबीचएकpeptidebondबनताहैतोइसकेपरिणामस्वरुपबननेवाले
compoundको_____कहतेहैंI
(xvii)Proteinsकेतीनglobalclassesहैं______proteins,_______proteins,और_______proteins
(xviii)proteinमेंमौजूदसभीcovalentbondsकाविवरणऔरproteinsकीpolypeptidechainsकेअमीनो
acidsकेlinearsequenceसेहमेंproteinके________structureकापताचलताहैI
(xix)Proteinmoleculeकेglobularthree-dimensionalshape,जोpolypeptidechainकीtwisting,
foldingऔरcompactpackingकेफलस्वरुपबनताहै,उससेproteinके_____structureकापताचलताहैI
(xx)Proteinsका______structureदोयाअधिकअलग-अलगproteinunits(अपने-अपनेtertiary
structureमें)केगठबंधनसेबनताहैऔरयहtertiarystructureसेऔरअधिकस्थिरहोताहैI
(xxi)_____testमेंproteinsकाalphaaminogroupninhydrinकेसाथreactकरकेएकcoloured
complexबनाताहैंजोdeepblueसेvioletpinkहोताहैI

21. 21
(xxii)Aminoacidsजिनमेंएकaromaticnucleusहोताहै,वेHNO3केसाथगर्मकरनेपरyellowcolour
का
nitroderivativesderivativeबनातेहैंऔरistestको_________testकहतेहैंI
(xxiii)_______testisaspecifictestfortyrosine.
(xxiv)_______testमेंtryptophanकाindolegroupglyoxylicacidसेconc.H2SO4कीउपस्थितिमें
purplecolorदेताहैI
(xxv)NitroprussideTestisaspecifictestforthesulfhydrylgroupcontainingaminoacid
________.
(xxvi)Serumtotalprotein_______testद्वाराऔरserumalbumin_________testद्वारामापतेहैंI
(xxvii)केवल________ऐसेenzymesहैंजोproteinsनहींहोतेI
(xxviii)Chemicalreactionsकेदौरानenzymes______नहींहोतेऔरबार-बारइस्तेमालहोतेहैंI
(xxix)किसीenzymeकेenzymaticallyinactiveproteinpartको_______कहतेहैंI
(xxx)एकenzymeकेउसnonproteinpartकोजिसकीआवश्यकताenzymeactivityकेलिएहोतीहै,उसे
________कहतेहैंI
(xxxi)______enzymeकाnonproteinorganiccofactorहोताहैजिसकीenzymeactivityकेलिए
आवश्यकताहोतीहैI
(xxxii)जबएकcofactorएकproteinयाenzymeसेtightlyboundहोताहैतोउसcofactorको_______
groupकहतेहैंI
(xxxiii)_________वोchemicalsubstanceहोताहैजिसकाtransformationएकenzymeद्वारा
catalyzeहोताहैI
(xxxiv)Enzymeकावोहिस्साजहाँcatalyticप्रक्रियाकेसारेeventsहोतेहैं,______siteकहलाताहैI
(xxxv)Enzymeactivityकीtraditionalunit____हैऔरSIunit______हैI
(xxxvi)किसीenzymeकेविभिन्नरूपजोsamereactionकोcatalyzeकरतेहैंकिन्तुउनकी
physico-chemicalpropertiesभिन्नहोतीहैंउन्हें__________कहतेहैंI
(xxxvii)Lactatedehydrogenaseenzymeके_____isoenzymesहोतेहैंI
(xxxviii)LDH-1कीमात्रा_____मेंसबसेअधिकहोतीहैजबकिLDH-5कीसबसेअधिकमात्रा_______
musclesऔर_____मेंहोतीहैI
(xxxix)Myocardiumमेंपायाजानेवालाcreatinekinaseकाisoenzyme________हैI
(xxxx)Serumcardiac_______कोMIकीdiagnosisहेतु'Goldstandard'biochemicalmarkerमाना
जाताहैI
Ans.(i)aminoacids,(ii)20,(iii)peptide,(iv)enzymes,(v)structural(संरचनात्मक),(vi)
lipoproteins,hemoglobin,(vii)antibodies,(viii)hormones,(ix)amino,carboxyl,(x)glycine,(xi)
zwitter(xii)isoelectric,(xiii)essential,(xiv)adequate,complete,(xv)soyabean,(xvi)dipeptide,
(xvii)fibrous,globular,membrane,(xviii)primary,(xix)tertiary,(xx)quaternary,(xxi)ninhydrin,
(xxii)Xanthoproteic,(xxiii)Millon's,(xxiv)Hopkins-Cole,(xxv)cysteine,(xxvi)Biuret,
Bromocresolgreen,(xxvii)ribozymes,(xxviii)नष्ट,(xxix)apoenzyme,(xxx)cofactor,(xxxi)
coenzyme,(xxxii)prosthetic,(xxxiii)substrate,((xxxiv)active,(xxxv)UयाIU,katal,(xxxvi)
isoenzymes,(xxxvii)पाँच,(xxxviii)heart,skeletal,liver,(xxxix)MB,(xxxx)Troponin
REFERENCES
1.LehningerPrinciplesofbiochemistry,seventhedition;DavidL.Nelson&MichaelM.
Cox.
2.NigamPK.Biochemicalmarkersofmyocardialinjury.IndJClinBiochem22(1);10-17,
2007.

22. 22
3.AydinS.etal.Biomarkersinacutemyocardialinfarction:currentperspectives.Vasc
HealthRiskManag15;1-10,2019.
Disclaimer:ThepicturesgiveninthetexthavebeendownloadedfromGoogleimagesandI
amthankfultothepersonswhohaveuploadedthesepictures.
Dr.P.K.Nigam
RetiredBiochemist