INACTIVATION OF HISTIDINE AMMONIA-LYASE FROM STREPTOMYCES-GRISEUS BY DICARBONYL REAGENTS

Histidine ammonia-lyase from Streptomyces griseus was inactivated by m ethylglyoxal and phenylglyoxal, dicarbonyl reagents known to react spe cifically with arginyl residues in proteins. The inactivation showed p seudo-first-order kinetics and could be prevented by protection with h istidinol phosphate, a competitive inhibitor of histidine ammonia-lyas e. Analysis of the amino acid composition of histidine ammonia-lyase a fter treatment with phenylglyoxal, together with the kinetics of inact ivation, suggested that inactivation was a consequence of specific rea ction with one or more essential arginyl residues at or near the activ e site of the enzyme.