Phase II conjugation reactions in xenobiotic metabolism increase drug water-solubility for excretion. Which Phase II reaction conjugates bile acids, bilirubin, and many drugs using UDP-glucuronic acid?
- A Sulfation by sulfotransferases (SULTs)
- B Acetylation by N-acetyltransferases (NATs)
- C Glucuronidation by UDP-glucuronosyltransferases (UGTs) ✓
- D Methylation by catechol-O-methyltransferase (COMT)
Correct answer: C. Glucuronidation by UDP-glucuronosyltransferases (UGTs)
Explanation
Glucuronidation is quantitatively the most important Phase II detoxification reaction; UGT enzymes transfer glucuronic acid from UDP-glucuronic acid to hydroxyl, carboxyl, amino, or thiol groups of substrates including bilirubin, bile acids, steroids, NSAIDs, and opioids, making them water-soluble for biliary or renal excretion. Neonates have immature UGT1A1 activity, leading to unconjugated hyperbilirubinemia (physiological jaundice of the newborn).
Reference: Harper's Illustrated Biochemistry, 32nd ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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