What are co-factors ? Describe its types.

Explanation

`-` Enzymes are composed of one or several polypeptide chains. Generally, non-protein constituents called co-factors are bound to the enzyme to make the enzyme catalytically active.
- The protein portion of the enzymes is called the apoenzyme.
- Three kinds of co-factors may be identified :
(1) Prosthetic groups (2) Co-enzymes (3) Metal ions.
(1) Prosthetic groups : Prosthetic groups are organic compounds they are tightly bound to the apoenzyme. e.g. peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to `H_2O` and `O_(2)` , haem (`Fe^(++)`) is the prosthetic group and it is a part of the active site of the enzyme.
(2) Co-enzymes : Are also organic compounds. They are associated temporarily with apoenzyme.
- They serve as co-factors in a number of different enzyme catalyzed reactions.
- Many co-enzymes have vitamins as their components e.g., co-enzyme nicotinamide
adenine dinucleotide (NAD) and NADP contain the vitamin niacin.
(3) Metal ions : Are essential in the activity of many enzymes which 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., zinc is a co-factor for enzyme carboxypeptidase.
Catalytic activity is lost when the co-factor is removed from the enzyme.