What is the part of an enzyme that is separated from its cofactor called?

The term that describes the part of an enzyme that is separated from its cofactor is called "apoenzyme." An apoenzyme is the protein component of an enzyme that requires a cofactor, which can be a metal ion or an organic molecule, to function properly. When the cofactor is removed, the apoenzyme cannot catalyze its specific biochemical reaction because it does not possess the necessary structural configuration to be active.

In contrast, a holoenzyme refers to the complete enzyme that includes both the apoenzyme and its associated cofactor, making it active and functional. Coenzymes, on the other hand, are a subset of cofactors that are organic molecules, often derived from vitamins, that aid enzymes in catalyzing reactions. The substrate is the reactant molecule that an enzyme acts upon during the biochemical reaction.

Understanding these distinctions is crucial in biochemistry and enzymology, as it highlights the importance of cofactors in enzyme activity and regulation.