Question

What is an enzyme co-factor?

Answer 1

Hint: The proteinaceous substances which do not undergo any change themselves but are capable of catalyzing biochemical reactions are called enzymes. Therefore, they are called biocatalysts. Enzymes are synthesized with the help of living cells. The substance itself is not used up or changed at the end of the reaction is known as the catalyst, and the phenomenon is known as catalysis.

Complete answer:
Cofactors are the non-protein constituents bound to the enzyme to make the enzyme catalytically active and the protein part of the enzyme is known as apoenzyme. A complete conjugate enzyme, consisting of an apoenzyme and a cofactor is called a holoenzyme.

There are three types of cofactors –
i) Prosthetic groups: They are organic compounds and are distinguished from other cofactors in that they are tightly bound to the apoenzyme. For example, in peroxidase and catalase, haem is the prosthetic group and it is the part of the active site of the enzyme.
ii) Coenzymes: They are also called organic compounds, but their association with the apoenzyme is only transient, usually occurring during the course of catalysis. It serves as a cofactor for a number of different enzyme-catalyzed reactions. The essential chemical compounds of coenzymes are vitamins. For example, NAD and NADP.
iii) Metal ions – A number of enzymes require metal ions for their activity 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 Cofactor for the proteolytic enzyme carboxypeptidase is Zinc (Zn).

Note: Enzymes are proteinaceous in nature and are composed of one or more polypeptide chains. Enzymes are of mainly two types –
i) Simple are those enzymes made up of protein only. They do not contain non-protein parts. E.g. pepsin, trypsin, etc.
ii) Conjugates are those enzymes made up of both proteins as well as non-protein parts.
 Catalytic activity is lost when the cofactors play crucial roles in the catalytic activity of the enzyme.