Apoenzyme

Definition

An apoenzyme is the protein component of an enzyme, which requires a cofactor to become fully active. Without its cofactor, an apoenzyme is inactive and unable to catalyze reactions.

5 Must Know Facts For Your Next Test

1. Apoenzymes are inactive on their own and require a non-protein cofactor to form a complete, active enzyme known as a holoenzyme.
2. Cofactors can be metal ions such as zinc or magnesium, or organic molecules called coenzymes.
3. The binding of the cofactor induces a conformational change in the apoenzyme that allows it to bind substrates and catalyze reactions.
4. Apoenzymes have specific sites that interact with cofactors, ensuring proper catalytic activity.
5. The deficiency of required cofactors can lead to dysfunctional enzymes and metabolic disorders.

Review Questions

• What is the difference between an apoenzyme and a holoenzyme?
• Why are cofactors essential for the activity of apoenzymes?
• What types of molecules can act as cofactors for apoenzymes?

Related terms

Holoenzyme: A complete enzyme consisting of an apoenzyme bound to its necessary cofactor.

Cofactor: A non-protein chemical compound or metallic ion required for an enzyme's biological activity.

Coenzyme: An organic molecule serving as a cofactor that binds to the enzyme temporarily during catalysis.