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

Histidine ammonia-lyase from Streptomyces griseus was inactivated by methylglyoxal and phenylglyoxal, dicarbonyl reagents known to react specifically with arginyl residues in proteins. The inactivation showed pseudo-first-order kinetics and could be prevented by protection with histidinol phosphate, a competitive inhibitor of histidine ammonia-lyase. Analysis of the amino acid composition of histidine ammonia-lyase after treatment with phenylglyoxal, together with the kinetics of inactivation, suggested that inactivation was a consequence of specific reaction with one or more essential arginyl residues at or near the active site of the enzyme.