Acetylation is a Phase II conjugation reaction important in the metabolism of sulfonamides, hydralazine and procainamide. What is the immediate acetyl group donor for N-acetyltransferase?

• A Acetyl phosphate
• B Acetyl-AMP
• C N-acetylcysteine
• D Acetyl coenzyme A ✓

Explanation

N-acetyltransferases transfer the acetyl group from acetyl coenzyme A onto amino, hydroxy or sulfhydryl groups of substrates. Acetylation is unusual among Phase II reactions because it frequently decreases water solubility, explaining crystalluria with sulfonamides in slow acetylators. N-acetylcysteine replenishes glutathione stores and has no donor role here, and neither acetyl phosphate nor acetyl-AMP serves as the donor in human NAT reactions.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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