Aminopeptidase Profiles of Lactic Streptococci

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Abstract
Aminopeptidase activities of cell-free extract from 11 strains of Streptococcus lactis and S. cremoris, used as starter bacteria in cheese manufacture, were determined with 54 synthetic substrates. Based on these aminopeptidase profiles, 11 strains were divided into 3 groups by cluster analysis. Enzymes involved in representative strains of each cluster (S. lactis 527, S. cremoris ML-14 and S. cremoris nTR) were separated partly by diethylaminoethyl-cellulose chromatography and compared for each enzyme''s optimum pH and the effect of various metal ions and chemicals. These strains have at least 6 aminopeptidases (dipeptidase specific for hydrophobic amino acid-x, dipeptidase for basic amino acid-x, prolinediaminopeptidase, aminopeptidase P (or prolidase), general aminopeptidase, and tripeptidase), although contents of enzymes vary among strains.