Comparison of cell surface proteinase activities within the Lactobacillus genus
1997
Whole cells of Lactobacillus delbrueckii subsp. bulgaricus CNRZ 397 ( Lb. bulgaricus CNRZ 397) are able to hydrolyse α- and β-caseins.
We have isolated a mutant of Lb. bulgaricus altered for growth in milk and unable
to hydrolyse α- or β-casein. Normal growth was restored by adding
amino acids or tryptone to milk. No significant difference between the peptidase activities of parent and mutant
strains was observed. The cell surface caseinolytic activities of three lactobacilli
species and Lactococcus lactis subsp. lactis ( Lc. lactis )
were compared. As expected, the characteristics of the cell surface proteinase activity of Lb. casei were similar to those of Lc. lactis . We showed that the cleavage specificities of the cell surface proteinase activities from lactobacilli were species-dependent and at least three
types of activity were distinguished. The regulation of the biosynthesis of cell surface
proteinase activities was medium-dependent and different within the Lactobacillus genus and even within the Lb. delbrueckii species. In contrast to Lb. bulgaricus , the cell surface proteinase activity of Lb. lactis was totally inhibited in a medium rich in peptides or amino acids. In contrast, the cell surface of Lb. helveticus probably displayed two proteinases with different cleavage specificities and with a biosynthesis
regulation sensitive to different medium components.
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