CHEMICAL MODIFICATION OF RAT-LIVER ARGINASE

Abstract

Chemical modifications were used to search for catalytically important residues of rat liver arginase. The results of carbamoylation, nitration and diazotization suggest that lysyl and tyrosyl residues are not involved in the catalytic function of arginase. The modification of 5-6 tryptophanyl residues by N-bromosuccinimide or 2-hydroxy-5-nitrobenzyl bromide led to .apprx. 90% inhibition of the enzyme activity. Photooxidation of 21 histydyl residues also led to considerable inactivation of arginase. The modification of tryptophanyl and histidyl residues did not cause dissociation of the enzyme into subunits.