3. Which enzyme can be a catalyst like perchloric acid in Baeyer-Villiger reaction
a. trypsin
b. flavin monoxygenase
c. chymotrypsin
d. alcohol dehydrogenase

Introduction
The Baeyer-Villiger reaction enzyme catalyst mimics perchloric acid’s role in oxidizing ketones to esters or lactones via oxygen insertion, a key organic transformation tested in CSIR NET Life Sciences and Chemistry exams. Perchloric acid activates peroxyacids for this rearrangement, and nature employs flavin-dependent enzymes for analogous biocatalysis. This article solves the MCQ while explaining each option for graduate-level clarity.​

Correct Answer

Flavin monooxygenase (option b) serves as the enzyme catalyst like perchloric acid in the Baeyer-Villiger reaction. These FAD-containing enzymes generate a peroxyflavin intermediate from NADPH and O₂, mimicking peroxyacid reactivity to insert oxygen into ketones through a Criegee-like mechanism.​

Option Analysis

• a. Trypsin: This serine protease hydrolyzes peptide bonds after lysine or arginine residues in the duodenum, aiding protein digestion into peptides and amino acids. It lacks oxidative capability for ketone rearrangement.​

• b. Flavin monooxygenase (correct): Known as Baeyer-Villiger monooxygenases (BVMOs), these enzymes catalyze ketone-to-ester conversions using flavin hydroperoxide, directly analogous to perchloric acid-promoted peroxyacid oxidations. The peroxyflavin attacks the carbonyl, enabling migratory aptitude-based rearrangement.​

• c. Chymotrypsin: Another serine protease, it cleaves peptide bonds after aromatic residues like phenylalanine or tyrosine, further digesting proteins in the small intestine. No role in oxidation or Baeyer-Villiger chemistry exists.​

• d. Alcohol dehydrogenase: This zinc-dependent enzyme oxidizes alcohols to aldehydes or ketones using NAD⁺/NADPH, reversing the Baeyer-Villiger substrate formation but not catalyzing the oxidation itself.​

Mechanism Comparison

Perchloric acid enhances peroxyacid nucleophilicity for Criegee intermediate formation, where the antiperiplanar group migrates. Flavin monooxygenases replicate this: NADPH reduces FAD, O₂ forms peroxyflavin, which adds to the ketone carbonyl, followed by migration and hydrolysis to ester/lactone. This biocatalytic efficiency suits industrial synthesis.