THE OCCURRENCE OF 2 INTRACELLULAR OLIGOENDOPEPTIDASES IN LACTOCOCCUS-LACTIS AND THEIR SIGNIFICANCE FOR PEPTIDE CONVERSION IN CHEESE

Two intracellular oligopeptide-preferring endopeptidases have been det ected in Lactococcus lactis. A neutral thermolysin-like oligoendopepti dase (NOP) has been purified to homogeneity and an alkaline oligoendop eptidase has been partially purified. The specificity of the oligoendo peptidases towards important intermediary cheese peptides, produced by chymosin action on the caseins, clearly differs from that of the cell -envelope proteinase (CEP). NOP is active under conditions prevailing in cheese and contributes to initial proteolysis in a young cheese. It probably plays a crucial role in the degradation of an important bitt er peptide in cheese, the beta-casein 193-209 fragment. The relatively low activity of the alkaline endopeptidase is further suppressed in c heese by the highly competitive actions of NOP and CEP.