holoensüümi

A holoenzyme is a complete, catalytically active enzyme consisting of a protein component called the apoenzyme and a non-protein cofactor. The cofactor is essential for the enzyme's activity, as it often participates directly in the chemical reaction catalyzed by the enzyme. If the cofactor is an organic molecule, it is often referred to as a coenzyme. If it is a metal ion, it is called a prosthetic group. The apoenzyme, by itself, is inactive. It is only when the cofactor binds to the apoenzyme that the holoenzyme is formed and gains its full enzymatic function. This binding can be transient, as with many coenzymes, or permanent, as with some prosthetic groups. The specific type of cofactor required varies greatly among different enzymes. For example, many dehydrogenases require NAD+ or FAD as coenzymes, while metalloenzymes utilize metal ions such as zinc, magnesium, or iron. The formation of a holoenzyme is a crucial step in regulating enzyme activity and can be influenced by the availability of the cofactor.