holozyme

A holozyme is a complete, catalytically active enzyme. It consists of two essential components: an apoenzyme and a cofactor. The apoenzyme is the protein portion of the enzyme, which is typically inactive on its own. The cofactor is a non-protein chemical compound that is required for the enzyme's activity. Cofactors can be inorganic ions, such as magnesium or zinc ions, or organic molecules called coenzymes, which are often derived from vitamins.

The apoenzyme provides the structural framework and the active site for the enzyme, but it lacks the specific chemical groups necessary for catalysis. The cofactor binds to the apoenzyme, either tightly (as a prosthetic group) or loosely, and contributes to the active site's functionality. This binding often induces a conformational change in the apoenzyme, enabling it to bind its substrate and perform its catalytic function efficiently. Without the appropriate cofactor, the apoenzyme cannot catalyze the reaction.

In essence, the holozyme represents the fully functional enzyme complex. The term emphasizes that both the protein and non-protein parts are necessary for the enzyme's biological role. Many enzymes in biological systems exist and function as holozymes. The study of holozymes is crucial for understanding enzyme mechanisms, kinetics, and regulation.