The following sequence alignment between several species sho

The following sequence alignment between several species shows many conserved residues that may take part in the catalytic function. The mutants R292G and R292A of the Ar-BVMO monooxygenase enzyme showed very small residual activities compared to the wild type enzyme. What is the catalytic role of this arginine residue considering the enzyme reaction mechanism?

Solution

ANS:

Baeyer–Villiger monooxygenases (BVMOs):

It is a flavin-containing enzyme, which are mainly participates in specific catalytic Baeyer-Villiger oxidation. In this reaction the carbonyl moiety of the substance was oxidized. This protein helps in conversion of ketones into esters and lactones. Heteroatom oxidations (nitrogen and sulfur) are also catalyzed by BVMO enzymes.

All BVMO enzymes can incorporate one oxygen atom into the substrate (oxygen atom inserts into C–C bond) while converting the other oxygen into water.

Arginine importance in BVMO:

The protein arginine residue reacts with Alfa or Beta dicarbonyl compounds to form cyclic derivatives.

The active sites of Arginine 292 residue can catalysis Ar-BVMO in Baeyer-Villiger reactions. so due to this activity arginine is crucial for Baeyer-Villiger reactions.

The active site Arginine 292 is required for its Baeyer Villiger activity. If the amino acids glycine or alanine are replaced in the place of arginine 292 the enzyme activity is greatly reduced or no Baeyer-Villiger activity.

Mutants R292A and R292G have no BV activity while still maintaining their S- and N- oxygenation capabilities.