EFFECT OF PEPTIDES FROM THE SEQUENCE-58-72 OF BETA-CASEIN ON THE ACTIVITY OF ENDOPEPTIDASE, AMINOPEPTIDASE, AND X-PROLYL-DIPEPTIDYL AMINOPEPTIDASE FROM LACTOCOCCUS-LACTIS SSP LACTIS MG1363

The K-i values for the inhibition of the 70 kDa intracellular, o-phenanthroline-sensitive endopeptidase from Lactococcus lactis ssp. lactis MG1363 by bovine beta-casein (CN) f58-72, beta-CN f58-70, beta-CN f60-68, beta-CN f60-70, and beta-CN f60-66 were 0.018, 0.01, 0.045, 0.150 and 0.28 mM, respectively. The 95 kDa aminopeptidase, which is also, sensitive to o-phenanthroline, from the cytoplasm of the same microorganism was inhibited by the above peptides but the corresponding K-i values were 3-10 times higher. The X-prolyl-dipeptidyl aminopeptidase from the same source, which is insensitive to o-phenanthroline, was not inhibited by any of the above peptides and in fact hydrolyzed beta-CN f60-66 and beta-CN f60-70. beta-Casein f58-72 did not inhibit thermolysin and was degraded by it. The results demonstrate that cheese ripening may be influenced by inhibitory peptides originating from beta-casein.