This document discusses the classification of enzymes by the International Union of Biochemistry. It states that enzymes are divided into 6 main classes - oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases - based on the type of chemical reactions they catalyze. Each enzyme is assigned a 4-digit code number indicating its class, subclass, and identity. The document also describes the three types of cofactors that can bind to enzymes and enable their catalytic activity: prosthetic groups, coenzymes, and metal ions.

1. DR.HARINATHAREDDY M.Sc, Ph.D.
Department of Microbiology
Sri krishnadevaraya University, Anantapur,
A,P, INDIA

2. • Thousands of enzymes have been discovered, isolated
and studied.

3. • Most of these enzymes have been classified into
different groups based on the type of reactions they
catalyse.
• Enzymes are divided into 6 classes each with 4-13
subclasses and named accordingly by a four-digit
number.

4. International Union of Biochemistry (IUB).
Based on their action they are divided into 6 major classes.
Each enzyme is assigned a 4 Digit code number.
 (i) the first number shows enzyme classes.
 Ii). the second figure indicates the subclass,
 (iii) the third figure gives the sub-subclass,
 (iv) the fourth figure is the serial number of the enzyme in its sub-
subclass.

5. 6 classes of enzymes:
 Oxidoreductases/dehydrogenases:
 Transferases:
 Hydrolases:
 Lyases:
 Isomerases
 Ligases

8. Oxidoreductases/dehydrogenases:
• Enzymes which catalyse oxido-reduction between two
substrates S1 and S2.

9. Transferases:
• Enzymes catalysing a transfer of a group, G (other than
hydrogen) between a pair of substrate S and S’.

10. Hydrolases:
• Enzymes catalysing hydrolysis of:
• ester,
• ether,
• peptide,
• glycosidic,
• C-C,
• C-halide
• P-N bonds.

11. Lyases:
• Enzymes that catalyse removal of groups from substrates
by mechanisms other than hydrolysis leaving double
bonds..

12. • Isomerases: Includes all enzymes catalysing inter-
conversion of optical, geometric or positional isomers.
• Ligases: Enzymes catalysing the linking together of 2
compounds, e.g
• catalyse joining of C-O, C-S, C-N, P-O etc.

13. Co-factors

15. • Enzymes are composed of one or several polypeptide
chains.
• In number of cases in which non-protein part called
cofactors are bound to the the enzyme to make the
enzyme catalytically active.
• Catalytic activity is lost when the co-factor is removed
from the enzyme.

16. • In these instances, the protein portion of the enzymes is
called the apoenzyme.
• Three kinds of cofactors may be identified:
• prosthetic groups,
• co-enzymes
• metal ions.

17. Three kinds of cofactors
• Prosthetic groups
• Co-enzymes
• metal ions

18. Prosthetic groups
• Prosthetic groups are organic compounds and are
distinguished from other cofactors in that they are
tightly bound to the apoenzyme.

19. Prosthetic groups
• For example: In peroxidase and catalase, which catalyze
the breakdown of hydrogen peroxide to water and
oxygen.
• In peroxidase and catalase haem is the prosthetic group
and it is a part of the active site of the enzyme.

20. Co-enzymes
• Co-enzymes are also organic compounds but their
association with the apoenzyme is only transient,
usually occurring during the course of catalysis.
• Coenzymes are vitamins.
• NAD and NADP contain the vitamin niacin.
 Nicotinamide adenine dinucleotide (NADH)
 Nicotinamide adenine dinucleotide phosphate (NADPH)

21. Metal ions
• A number of enzymes require metal ions for their
activity.
• Metal ions form coordination bonds with side chains at
the active site and at the same time form one or more
coordination bonds with the substrate,
• e.g: Zn is a cofactor for the proteolytic enzyme carboxy-
peptidase.

22. • The technological function of carboxypeptidase is to
release C-terminal amino acids from proteins

23. Thank you