What is the complete enzyme including its protein portion and any necessary cofactors called?

The complete enzyme, which includes its protein portion as well as any necessary cofactors, is referred to as a holoenzyme. The holoenzyme represents the functional form of the enzyme, as it contains all components required for enzymatic activity. The protein portion alone, without its cofactors, is termed an apoenzyme, but it would not be active in that form. Cofactors, which can be metal ions or organic molecules, contribute to the overall structure and function of the holoenzyme, enabling it to catalyze biochemical reactions effectively.

Coenzymes are specific types of cofactors that are often organic molecules derived from vitamins and play a key role in assisting the enzyme. However, they do not account for the entire structure of the enzyme. Proenzyme, or zymogen, refers to the inactive precursor of an enzyme that requires a biochemical change to become active, thus not defining the complete enzyme structure.

Understanding these terms is crucial for grasping how enzymes function and the roles that different components play in enzymatic reactions.