Classification Of Enzymes

 CLASSIFICATION OF ENZYMES

• According to International Union of Biochemistry, enzymes classified into 6 classes called as enzyme code (EC)-

1. Class I enzyme (EC-1)– Oxidoreductases-

oxidation- reduction reaction. Subdivided-

 Oxidases– L- amino oxidase, xanthine oxidase, Tyrosinase.

 Dehydrogenases (DH)-

• Pyruvate DH, malate DH- NAD+
• Glucose -6- P- DH, gluconate dehydrogenase- NADP+
• Succinate DH- FAD+

Oxygenases-

 2. Class II enzyme (EC-2)- Transferase-

• transfer of functional group from donor or acceptor.
• E.g. Amino transferase ( transaminase)
• Kinase (hexokinase)
• Transketolase
• Transadolase
• Transcarboxylase

 3. Class III enzyme (EC-3)- Hydrolases-

• hydrolytic cleavage of C-C, C-O, C-N and other covalent bond.
• E.g. Urease

 4. Class IV enzyme (EC-4)- Lyases-

• splits substrate molecule by non-hydrolytic process.
• e.g.- Fumarase

 5. Class V enzyme (EC-5)- Isomerases-

• Geometric or structural changes within a molecule.
• E.g. Racemases

 6. Class VI enzyme (EC-6)- Ligases- 

• Binding two compunds together from source of energy ATP.
• E.g. synthatases, caboxylases. 
• According to IUB, EC number consist of 4 digits-

1. First digit- main class
2. Second digit- subclass
3. Third digit- sub-subclass
4. Fourth digit- individual enzymes

Exam Question

• According to International Union of Biochemistry, enzymes classified into 6 classes called as enzyme code (EC)
• A/c to IUB classification, Fourth digit- individual enzymes
• Class I enzyme (EC-1)- Oxidoreductases- oxidation- reduction reaction.
• Ligases- binding two compunds together from source of energy ATP.
• Oxireductases- Hydroperoxidases- Peroxidases, catalases.
• Hydrolases make use of water cleave a single molecule into two molecules.