Question

The protein part of an enzyme is called _______

• A. Apoenzyme
• B. Coenzyme
• C. Holoenzyme
• D. Cofactor

Hint:

Apoenzyme is the protein part; cofactor is the non-protein part; holoenzyme is the complete active enzyme.

Answer 1

The Correct Option is A

The question is asking about the terminology used for the protein component of an enzyme. To answer this, let's understand some basic enzyme terminology:

1. Apoenzyme: This is the protein component of an enzyme without its cofactor. It is inactive until it binds with a cofactor to form a complete enzyme.
2. Coenzyme: These are organic molecules that bind to the enzyme and assist in enzyme activity. Coenzymes are a type of cofactor.
3. Holoenzyme: This refers to the active form of an enzyme, which includes the apoenzyme and its associated cofactor(s).
4. Cofactor: These can be metal ions or organic molecules (such as coenzymes) that are necessary for the biological activity of some enzymes. Cofactors can be bound tightly or loosely to the enzyme.

Given the definitions above, the correct answer to the question is "Apoenzyme", as it is the term specifically used for the protein part of an enzyme. Let's justify why the other options are incorrect:

1. Coenzyme and Cofactor: These are not necessarily protein parts but are instead auxiliary molecules or ions that help the enzyme function.
2. Holoenzyme: This includes the apoenzyme plus its cofactor, making it active, not just the protein component.