LOCALIZATION OF AMINOPEPTIDASES IN STREPTOCOCCUS-SANGUIS STRAIN-903

The presence of aminopeptidases in the cytoplasm, in the cell wall, and in the cytoplasmic membrane fractions of Streptococcus sanguis 903 was demonstrated by isoelectric focusing in combination with enzyme-staining procedures. The cytoplasm and the cell wall both had two aminopeptidases (pI 4.25 and 4.3) with broad substrate specificities and one enzyme (pI 4.2) specific for arginine substrates. The former enzymes were both stimulated by Co2+ ions; the latter enzyme had no metal cofactor. The cytoplasmic membrane aminopeptidase (pI 4.65) was arginine specific and was not stimulated by metal ions. © 1990 Springer-Verlag New York Inc.