Question

Holoenzyme is produced by
A. Combined coenzyme and apoenzyme
B. Only prosthetic group
C. Only protein part
D. Only cofactor

Answer 1

Hint: Enzymes are the catalysts that accelerate the rates of biological reactions. Each enzyme is specific in its function and acts only in a particular metabolic reaction. With the exception of a small group of catalytic RNA molecules (Ribozymes), all enzymes are proteins.

Complete answer:
• Holoenzyme is a complete and catalytically active enzyme consisting of protein part (apoenzyme) together with its bound coenzyme and/or metal ions.
• A coenzyme or metal ion (non-protein part) that is very tightly or even covalently bound to the enzyme protein is called a prosthetic group.
• The protein part of holoenzyme is called the apoenzyme or apoprotein. It is the inactive form of enzyme which requires binding of inorganic or organic cofactor.
• Some enzymes do not require chemical groups for activity other than their amino acid residues. Some require an additional chemical component known as cofactor.
• Cofactors can either be inorganic ions of iron, magnesium, etc. or a complex organic or metallo-organic molecule called a coenzyme.

Hence, the correct answer is option (A).

Additional information:
Enzymes, like other proteins, have molecular weights ranging from about 12,000 to more than 1 million. Some enzymes require no chemical groups for activity other than their amino acid residues. The catalytic activity depends on the integrity of an enzyme’s native protein conformation. The primary, secondary, tertiary and quaternary structures of protein enzymes are essential to their catalytic activity. If an enzyme is broken down to its component amino acids, its catalytic activity is always destroyed.

Note: Coenzymes act as transient carriers of specific functional groups. Most are derived from vitamins, organic nutrients required in small amounts in the diet. Some enzymes require both coenzyme and metal ions for activity.