Enzymes(introduction,nomenclature and classification)

Enzymes(introduction, nomenclature, and IUB classification)

1. Enzymes
Introduction, Nomenclature & I.U.B. classification
Presented by-Shubhrat Maheshwari
Assistant Professor
RRSCOP, Amethi

2. Introduction
1.Enzymesareasubstanceproducedbyalivingorganismwhichactsasacatalysttobringabouta
specificBiochemicalreactionsoalsocalledasBio-catalyst.
2.Enzymesarebiologicalmolecules(typicallyproteins)thatsignificantlyspeeduptherateof
virtuallyallofthechemicalreactionsthattakeplacewithincells.Theyarevitalforlifeandservea
widerangeofimportantfunctionsinthebody,suchasaidingindigestionandmetabolism.
3.Enzymesaremadefromaminoacids,andtheyareproteins.Whenanenzymeisformed,itis
madebystringingtogetherbetween100and1,000aminoacidsinaveryspecificanduniqueorder.
Thechainofaminoacidsthenfoldsintoauniqueshape.

4. Properties of enzymes
1.Enzymesareproteinmacromolecule.
2.Theyareorganicbiocatalyst(simpleorconjugated).
3.Theyrequiresmallquantityforthebiologicalaction.
4.Theiractivitydependsonthetemperature(optimizedtemp.35℃-40℃)andchangesinhydrogenion
concentration(pH).
5.Theyarespecificforbondsorlinkagelikeester,orglycosidee.g.Esteraseactonesterbond
6.Theyactononlyonetypeofspecificsubstrate(e.g.ureasedecomposeurea).

5. Properties of enzymes
7.Theyalwaysproducethesameendproducts.
8.Theyarereusable.
9.Proenzymesareinactivebeforethestartofreaction.
10.Someenzymesrequiresascofactorforproperfunctioning.Cofactorsarenon-proteinpartderivedfrom
niacin,riboflavinetc.whichisboundwithintheenzymemolecules.
11.Theylowertheactivationofenergysoreactionsoccuratmildtemperatureinallleavingcells.
12.Manyenzymesarestereospecifice.g.LaminoacidoxidaseactonlyontheL.aminoacidnotonD-amino
acid.

6. Nomenclature of Enzymes
•The nomenclature of first discovered enzymes was named according to their sources by adding suffix -inlike
pepsin, trypsin etc.
Enzyme acted upon the substrate
•Themoleculeuponwhichenzymeactsisknownassubstrate.Namingofanenzymebyaddingthe
suffix–aseinthenameofthesubstratewhichiscatalyzedbytheenzyme.
•Forexample,enzymescatalyzinglipidswerenamedlipases,nucleicacidsasnucleasesandsoon.
•Afewofthenameswereevenmorespecificlikemaltase(actinguponmaltose),tyrosinase
(tyrosine),sucrase(sucrose)etc.,

8. Nomenclature of Enzymes(contd.)
Type of reaction catalyzed by enzyme :
•The enzymes are highly specific to the reaction they catalyze.
•Hence, this has been necessary in naming them by adding suffix-asein the name of the reaction;
•for example
•hydrolases (catalyzinghydrolysis),
•isomerases (isomerization),
•oxidases (oxidation),
•dehydrogenases (dehydrogenation),
•transaminases (transamination),
•Phosphorylases (phosphorylation) etc.,

9. Nomenclature of Enzymes(contd.)
Substance that is synthesized :
•A few enzymes have been named by adding the suffix –aseto the name of the substance
synthesized, viz., fumarase that forms fumarate irreversibly from L-malate.

10. Enzyme classification (IUB Classification)
•In 1961, International Union of Biochemistry (I.U.B.) used this criterion as a basis for the classification and
naming of enzymes. Although complicated, the I.U.B. system is precise, descriptive and informative.
•Enzymes are classified according to the type of reaction they catalyze.
•According toInternationalUnion of Biochemistry and Molecular Biology (IUBMB) system, enzymes are
classified into seven major classes.
a.The reactions and the enzymes catalyzing them are divided into 7 major classes, each with 4 to 13
subclasses.
b.Each enzyme name has two parts-the first part is the name of the substrate and the second part which ends
in suffix –ase, indicates the type of the reaction catalyzed.

11. c.Each enzyme has been allotted a systemic code number called Enzyme Commission (E.C.)
number. The E.C. number for each enzyme consists of a series of numbers at 4 places:
-First digit represents the class-classifies the enzyme based on its reaction.
-Second digit stands for the subclass-indicates the type of group involved in thereaction.
-Third digit is the sub-subclass or subgroup-indicates substrate on which group acts.
-Fourth digit gives the number of particular enzymes in the list-indicates the serial number of
individual enzyme.

12. •For example –
➢Thus E.C.2.7.1.1 represents class 2 (a transferase), subclass 7 (transfer of phosphate), sub-subclass 1 (an
alcohol group as phosphate acceptor). The final digit denotes the enzyme, hexokinase or ATP:
•D-hexose-6-phosphotransferase. This enzyme catalyzes the transfer of phosphate from ATP to the hydroxyl
group on carbon 6 of glucose.
ATP + D-hexose hexokinase ADP+ Hexose-6-phosphate

14. 7.Translocases catalyse the movement of ions or molecules hydron H+, inorganic anions,
membrane or their separation within membranes. Inorganic cations etc.