May 30, 2024

IUB classification of enzymes

IUB classification of enzymes

The International Union of Biochemistry and Molecular Biology (IUBMB) classifies enzymes based on the type of chemical reaction they catalyze. This classification system is based on a numerical system consisting of four digits, with each digit representing a different aspect of the enzyme’s function.

The first digit indicates the type of reaction catalyzed:

  1. Oxidoreductases
  2. Transferases
  3. Hydrolases
  4. Lyases
  5. Isomerases
  6. Ligases

The second digit indicates the substrate acted upon:

  1. Oxidoreductases acting on CH-OH group donors
  2. Oxidoreductases acting on a sulfur group donor
  3. Oxidoreductases acting on nitrogenous group donors
  4. Oxidoreductases acting on other acceptors
  5. Transferases transferring alkyl or aryl groups, other than methyl groups
  6. Transferases transferring nitrogenous groups
  7. Transferases transferring phosphorus-containing groups
  8. Transferases transferring sulfur-containing groups
  9. Transferases transferring glycosyl groups

The third digit indicates the type of bond formed or broken:

  1. Hydrolysis
  2. Transfer of an aldehyde or ketone group
  3. Transfer of an acyl group
  4. Phosphorolytic cleavage of an ester or anhydride bond
  5. Carbon-carbon lyases
  6. Carbon-oxygen lyases
  7. Carbon-nitrogen lyases
  8. Phosphoric-ester hydrolases
  9. Phosphoric-anhydride hydrolases
  10. Sulfuric-ester hydrolases
  11. Carbon-phosphorus lyases
  12. Peptide hydrolases
  13. Other hydrolases

The fourth digit is used to indicate a subclassification of the enzyme based on further information about its substrate, reaction mechanism, or other characteristics.

For example, the enzyme lactate dehydrogenase has the classification number, indicating that it is an oxidoreductase (1) that acts on CH-OH group donors (1) by transferring electrons to a coenzyme (1), and that it acts specifically on lactate as a substrate (27).

First Year Pharm D Subjects Syllabus, Notes, PDF Books, MCQ

1.1Human Anatomy and Physiology
1.3Medicinal  Biochemistry
1.4Pharmaceutical Organic Chemistry
1.5Pharmaceutical Inorganic Chemistry
1.6Remedial Mathematics/ Biology

Suggested readings: