Question

What are the types of cofactors? Explain each of them.

Answer 1

1. Many enzymes require non-protein components called cofactors for their efficient activity. Cofactors may vary from simple inorganic ions to complex organic molecules. They are of three types: inorganic ions, prosthetic groups and coenzymes.
2. Holoenzyme: Active enzyme with its non-protein component.
3. Apoenzyme: The inactive enzyme without its non-protein component.
4. Inorganic ions help to increase the rate of the reaction catalysed by enzymes. Example: Salivary amylase activity is increased in the presence of chloride ions.
5. Prosthetic groups are organic molecules that assist in the catalytic function of an enzyme. Flavin adenine dinucleotide (FAD) contains riboflavin (Vit B₂), the function of which is to accept hydrogen. ‘Haem’ is an iron-containing prosthetic group with an iron atom at its centre.
6. Coenzymes are organic compounds that act as cofactors but do not remain attached to the enzyme. The essential chemical components of many coenzymes are vitamins, eg. NAD, NADP, Coenzyme A, ATP.