The active enzyme system formed by an apoenzyme plus a non-protein cofactor is called the holoenzyme.

The active enzyme system formed by an apoenzyme plus a non-protein cofactor is called the holoenzyme.

• A. Apoenzyme
• B. Coenzyme
• C. Holoenzyme
• D. Proenzyme

Answer: (C)

When the protein part of an enzyme (the apoenzyme) binds a non-protein helper, the whole complex becomes capable of catalysis. This complete, active form is called the holoenzyme. Without the cofactor, the apoenzyme remains inactive because the active site isn’t properly formed. The non-protein helper can be an inorganic ion or an organic molecule (a coenzyme). A proenzyme, by contrast, is an inactive precursor that requires activation steps other than just binding a cofactor. So the described active enzyme is the holoenzyme.

When the protein part of an enzyme (the apoenzyme) binds a non-protein helper, the whole complex becomes capable of catalysis. This complete, active form is called the holoenzyme. Without the cofactor, the apoenzyme remains inactive because the active site isn’t properly formed. The non-protein helper can be an inorganic ion or an organic molecule (a coenzyme). A proenzyme, by contrast, is an inactive precursor that requires activation steps other than just binding a cofactor. So the described active enzyme is the holoenzyme.