Most Important Phase-II Reaction
The most important phase-II biotransformation reaction applicable to most drugs is:
- Acetylation
- Glycine conjugation
- Sulfate conjugation
- Glucuronidation — Correct Answer
Explanation:
Correct Answer: Glucuronidation
Glucuronidation is the most important phase-II reaction — most drugs including endogenous steroids and bile pigments undergo this reaction. The source of glucuronide is UDPGA (UDP-glucuronic acid) through the enzyme glucuronyl transferase.
Key Facts
- Glucuronide conjugation takes place in microsomes.
- Product is highly soluble — excreted by urine (if MW <300–500) or via bile (if MW >500).
- Beta-glucuronidase in the intestine may liberate the active drug → reabsorbed → enterohepatic recirculation → longer duration of action.
Phase-II Reactions in Order of Importance
Glucuronidation > Sulfate conjugation > Acetylation > Methylation > Glycine conjugation > Glutathione conjugation.
📚 About this Topic — Veterinary Pharmacology and Toxicology
This multiple choice question is from Veterinary Pharmacology and Toxicology, Veterinary Science. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Veterinary Pharmacology and Toxicology to strengthen your preparation.
