NOMENCLATURE AND CLASSIFICATION OF ENZYMES

 

NOMENCLATURE AND CLASSIFICATION OF ENZYMES

Enzymes are generally named by adding “ase’ to the root indicating the substrate on which the enzyme acts. The International Union of Biochemistry report of 1962 contain a scheme for enzyme classification. Enzymes have been divided into 6 groups.

01. Oxireductases   dehydrogenases:  Enzymes which catalyze oxidation reduction reactions involving transfer for electrons/H⁺ from one molecule to another, in these reactions one compound is oxidized and the other is reduced.

                               Alcohol + NAD-----Aldehyde + NADH₂

02. Transferases: These enzyme catalyse the transfer of specific group other than hydrogen from one substrate to another.

Example: kinase catalyses the phosphorylation of substrate by transferring phosphate group from ATP.

03. Hydrolysis: These enzymes catalyze the breakdown of larger molecules in to smaller molecules with the addition of water. These bring hydrolysis of ether, peptide and ester.

                      Sucrose + H₂O ---------- Glucose + Fructose

04. Lyases: These enzyme catalyze the cleavage of substrate in to two parts, without the use of water or removal of group without hydrolysis. A double bond is formed at the place of removal of group.

Example: Decarboxylase, carbonic anhydrase, etc.

05. Isomerase: These enzymes catalyze the rearrangement of molecular structure to form isomers. Isomers are the molecular compounds that are similar in having the same molecular formula but have different arrangement of atoms. Example: Isomerase

06. Ligases: These enzymes catalyse covalent bonding of two substrates to form a large molecule. They catalyze joining of C-O, C-S, P-O bond by using ATP as energy source.

Example: RUBP carboxylase, phosphophenol pyruvate (PEP)