Question

The protein part of the enzyme is
(a) Prosthetic group
(b) Apoenzyme
(c) Holoenzyme
(d) Zymogen

Answer 1

The protein part of the enzyme, by combining with a coenzyme, forms an active enzyme system and determines the specificity of this system for a substrate. The protein section, in a complete enzyme, is formed along with a cofactor.

Complete Step by Step Answer: Enzymes are composed of one or several polypeptide chains but many enzymes exhibit the catalytic activity only in association with certain non- protein substances are called cofactors. In these enzymes, the protein portion is known as apoenzyme.
Enzymes are proteins or in conjugation with some non- protein materials called cofactors (except few). The enzyme catalyzes all the chemical reactions that occur in the living world.
Three types of cofactors are identified:
- Prosthetic group: They are organic compounds and are tightly bound to apoenzyme. For example, haem is the prosthetic group in peroxidase and catalase enzymes that catalyze the breakdown of hydrogen. Haem is a part of the active site of the enzyme.
- Co- enzyme: They are also organic compounds but their association with the apoenzyme lasts for a short period of time, usually occurring during catalysis.
- Metal ions: A number of enzymes require metal ions in their activity which forms coordination bonds.
So, the answer is ‘(b) Apoenzyme’.

Note: - An apoenzyme and its cofactor together are known as the holoenzyme. - These enzymes catalyze the biochemical reactions in the living cells, hence called biocatalysts. - When the cofactor is removed from the enzyme, catalytic activity is lost, which shows that it plays a vital role in the enzyme's catalytic activity.