Holoenzyme

Definition

A holoenzyme is a biochemically active enzyme complex that includes both an apoenzyme (protein portion) and its necessary cofactor(s), which can be either metal ions or organic molecules. It is the fully functional form of the enzyme, capable of catalyzing reactions.

5 Must Know Facts For Your Next Test

1. Holoenzymes consist of an apoenzyme and one or more cofactors.
2. The apoenzyme alone is inactive and requires cofactors to become a holoenzyme.
3. Cofactors can be metal ions like Mg2+ or organic molecules such as vitamins.
4. Holoenzymes are crucial for metabolic pathways, enabling specific biochemical reactions.
5. The formation of a holoenzyme ensures proper substrate binding and catalysis.

Review Questions

• What components make up a holoenzyme?
• Why is an apoenzyme inactive without its cofactors?
• How do cofactors assist in the enzymatic activity of holoenzymes?

Related terms

apoenzyme:

The protein component of an enzyme, which requires a cofactor to become active.

cofactor:

A non-protein chemical compound that is required for an enzyme's biological activity.

coenzyme:

An organic molecule serving as a cofactor, often derived from vitamins.