CHEMICAL MODIFICATION OF HISTIDINE RESIDUE OF N-ACYL-D-GLUTAMATE AMIDOHYDROLASE FROM PSEUDOMONAS SP 5F-1

N-Acyl-D-glutamate amidohydrolase (D-AGase) from Pseudomonas sp. 5f-1 was inactivated by diethyl pyrocarbonate (DEP). The chemical modificat ion by DEP showed a difference spectrum at 246 nm due to the N-carbeth oxyhistidine residue. Removal of the carbethoxy group from inactivated enzyme with hydroxylamine restored enzyme activity. The inactivation by DEP proceeded with pseudo-first-order kinetics, and was protected i n the presence of the substrate N-acetyl-D-glutamate (Glu), or the com petitive inhibitor sodium alpha-ketoglutarate (alpha-KGA). These resul ts suggest the presence of an essential histidine residue at or near o f the active site of the enzyme.