CHARACTERIZATION OF MEMBRANE-ASSOCIATED ARGININE AMINOPEPTIDASE IN STREPTOCOCCUS-SANGUIS 903

Extracts of cytoplasmic membranes of Streptococcus sanguis 903 were analyzed for aminopeptidase activity by isoelectric focusing in polyacrylamide gel and enzyme staining with 16 different aminopeptidase substrates. A single aminopeptidase with specificity for aminoterminal arginine was detected. The enzyme was stimulated by dithiothreitol and β-mercaptoethanol. Urea, sodium dodecyl sulfate (SDS), and p-chloromercuribenzoate were inhibitory. Metal ions had little or no effect on activity, except that Hg2+, Cu2+, and Ni2+ were inhibitory. The pH optimum for activity was at 7.2. The molecular mass estimated by SDS-polyacrylamide gel electrophoresis was 170 kDa. © 1990 Springer-Verlag New York Inc.