Identification of amino acid residues essential for enzyme activity of sheep liver 5,10-methylenetetrahydrofolate reductase

Abstract

Sheep liver 5, 10-methylenetetrahydrofolate reductase was subjected to specific chemical modification with phenylglyoxal, diethyl pyrocarbonate and N-bromosuccinimide. The second-order rate constants for inactivation were calculated to be 54 M^-1 min^-1, 103 M^-1 . min^-1 and 154 M^-1 . min^-1 respectively. This inactivation could be prevented by incubation with substrates or products, suggesting that the residues modified, namely arginine, histidine and tryptophan, are essential for enzyme activity.