Skv Enzyme Kinetics and Principles of Enzyme Inhibition

The content includes the general introduction of enzymes their basic classification. Enzyme kinetics is described with a short view of Michaelis menten constants. Factors affecting the kinetics of enzymes are also discussed. Principles of enzyme inhibition are discussed with a few examples.
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1. EnzymE kinEtics
&
PrinciPlEs of EnzymE inhibitors
Presented by: Sachin Kumar Vishwakarma
M.Pharm(Pharmaceutical Chemistry )
Presented to: Ms. GeetaMishra
Sr. Assistant Professor, BBDNIIT, Faculty of
Pharmacy
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2. introDUction
Enzymes:Enzymesarenature’sbiologicalcatalysts
possessingtheabilitytopromotespecificchemical
reactionsunderthemildconditionsthatprevailinmost
livingorganisms.
Theyareallproteinsbutrangewidelyintheirsizefromas
fewas60–70aminoacidresiduesasinRNasetoasmany
asseveralthousand.
Thecatalyticpropertiesofanenzymeareoften
dependentuponthepresenceofnonpeptidemolecules
calledcofactorsorcoenzymes,alsoknownasProsthetic
group.
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3. Enzymesarecharacterisedbytheirspecificity(bond
specificity,Stereospecificity,groupspecificity)fora
particulartypeofchemicalreaction.
Theturnovernumberisthemaximumnumberofmoles
ofsubstratethatcanbeconvertedtoproductper
moleofenzymeinunittime.Ithasunitsofreciprocal
timeinseconds.Itsvaluesrangefrom1to107Second
inverse.
Someenzymesexistinmultipleformscalledisoenzymes
orisoformsthatdifferinaminoacidsequence.
Someenzymesthatpromoteconsecutivereactionsina
metabolicpathwayassociatetoformamultienzyme
complex.
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4. clAssificAtion of EnzymEs
Byinternationalconvention,eachenzymeisclassified
intooneofsixgroupsonthebasisofthetypeof
chemicalreactionthatitcatalyses.
1.Oxidoreductases-reductases,oxidases
2.Transferases-kinases,aminotransferases
3.Hydrolases-peptidases,esterases
4.Lyases-enolase,aldolase
5.Isomerases-phosphoglucomutaseglucose-6-
phosphateisomerase
6.Ligases(synthases)-carbamoylphosphatesynthase,
DNAligase
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5. EnzymE kinEtics
Enzymekineticsisthestudyofthechemicalreactions
thatarecatalysedbyenzymes.
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6. Mathematical expression of enzyme action, developed
by Leonor Michaelisand Maud Mentenin 1913 ,two
constants,V
max
andK
m
, play an important role.
The maximal velocity, or V
max
, is the rate of the reaction
under these conditions.
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7. MichaelisConstant(K
m
)describesthesubstrate
concentrationatwhichhalftheenzyme'sactivesites
areoccupiedbysubstrate.
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8. EFFECT OF TEMPERATURE: The initial rate of an
enzyme reaction varies with temperature according
to the Arrhenius equation:
rate =Ae-(E/RT)
•A is a constant known as the pre-exponential factor,
•E is the activation energy (J mol1),
•R is the gas constant (8.2 J mol1 K1), and
•T is the absolute temperature (K).
EFFECT OF pH: Due to isoelectric point enzyme get
charged so the pH should be optimum .
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9. PrinciPlEs of EnzymE inhibitors
Enzymes represent the best known biochemical catalyst,
because they are uniquely designed to carry out specific
biochemical reactions in a highly efficient manner.
Enzymes bound to substrate and form a complex.
catalysis
Enzyme product -complex
Dissociation of product and liberation of enzyme .
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10. PrinciPlEs
1.Reversible enzyme inhibition: two types
I.Competitiveinhibition
II.Non-competitiveinhibition
2.Irreversible enzyme inhibition
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11. rEvErsiblE EnzymE inhibition
I.Competitive inhibition: requires that the inhibitor
competes with the substrate for binding to the
enzyme at active sites, and this binding is manually
exclusive.
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12. II.Non-competitive inhibition:
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13. Examples of reversible enzyme inhibition
Inhibition of HIV –reverse transcriptase –Azidothymidine
Cancer therapy –DHFR inhibitors-Methotrexate
Angiotensin Converting Enzyme inhibition –Enalapril
Acetylcholinesterase inhibition-Physostigmin
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14. irrEvErsiblE EnzymE inhibition
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15. Examples of irreversible enzyme inhibition
Inhibition of Beta-lactamase by Clavulanic acid .
GABA-transaminase inhibition by Gabaculine.
5Alfa reductase inhibition by Finasteride
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