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Aminopeptidases highly specific for glutamyl residues from Neisseria meningitidis and Moraxella urethralis.

ABSTRACT

Cell-associated glutamyl aminopeptidase activity was detected in several strains of Neisseria meningitidis and Moraxella urethralis grown in liquid culture. Enzymatic activity was released from washed cells by ultrasonic treatment and monitored fluorometrically by measuring the release of aryl groups from 17 different aminoacyl-beta-naphthylamides. Substrates containing a glutamyl moiety were readily hydrolyzed by both N. meningitidis and M. urethralis. Glutamyl aminopeptidase activity was partially purified from crude sonicates by means of ion-exchange and gel chromatography, and samples were examined by polyacrylamide gel electrophoresis. Kinetic and pH studies were performed to partially characterize activities. The molecular weight of the M. urethralis enzyme was approximately 88,000, whereas the apparent molecular weight of the N. meningitidis enzyme was shown to be in excess of 200,000. M. urethralis produced two glutamyl aminopeptidases, one specific for a gamma-glutamyl moiety, the other specific for an alpha-glutamyl moiety. In contrast, N. meningitidis produced a single glutamyl aminopeptidase which hydrolyzed alpha- and gamma-glutamyl-substituted beta-naphthylamides.