Question

The enzyme, which is usually secreted in the inactive state, is called

• A. zymogen
• B. isoenzyme
• C. apoenzyme
• D. coenzyme

Answer 1

The correct option is A zymogen

Zymogens are the precursors of enzymes. They are not active on their own but become active after conversion. Usually, a prefix- pro or suffix- ogen is added to their name to denote that they are zymogens.

Isoenzymes are distinct physical forms of some enzyme that can catalyse the same reaction. The difference noted in different forms of a single enzyme may be in their quaternary structure. Various isoenzymes are found in nature. For example - lactic dehydrogenase occurs in many isoforms in man.

An enzyme consists of a protein part called apoenzyme and a non-protein part called the cofactor. The apoenzyme and cofactor together form holoenzyme. The cofactor can be either inorganic ions, organic or metal-organic molecules complexes called coenzymes. A coenzyme or metal ion bonded to the protein is called the prosthetic group.