Peptide hydrolase system of lactic acid bacteria isolated from Serra da Estrela cheese

Lactobacillus paracasei subsp. paracasei ESB 230, Leuconostoc mesenteroides subsp. mesenteroides ESB 136, Lactococcus lactis subsp. lactis ESB 117 and Enterococcus faecium ESB 50, previously isolated from certified Serra da E strela cheeses, were tested for their aminopeptidase, dipeptidyl aminopepti dase, endopeptidase, dipeptidase and carboxypeptidase activities. The crude cell-free extracts (CFE) of Lb. paracasei ESB 230 exhibited the highest am inopeptidase activity, followed by CFE of Leuc. mesenteroides ESB 136 and, at last, by CFE of L. lactis ESB 117; the aminopeptidase activity in CFE of Ent. faecium was practically non-existent. The four CFE studied also showe d appreciable carboxypeptidase activities, although these were lower than t heir dipeptidase counterparts; in addition, their dipeptidyl aminopeptidase and endopeptidase activities were lower than their aminopeptidase activiti es. Dipeptides consisting of hydrophobic amino acid residues (i.e. leucine, methionine and phenylalanine) were more rapidly attacked by all CFE than t hose with hydrophilic amino acid residues. The peptide hydrolase system of CFE of Lb, paracasei ESB 230 was qualitatively quite similar to, but quanti tatively more active than that of CFE of Leuc. mesenteroides ESB 136 (excep t for the endopeptidase); additionally, the CFE of L, lactis ESB 117 and of Ent, faecium ESB 50 were quite distinct from each other, and from the othe r two CFE tested. (C) 2001 Elsevier Science Ltd. All rights reserved.