The influence of whey proteins on peptidase activities of Lactococcus lactis ssp. cremoris AM1

The effect of the native whey proteins α-lactalbumin (α-La), β-lactoglobulin (β-Lg) and bovine serum albumin (BSA) on the aminopeptidase activity of Lactococcus (Lc.) lactis spp. cremoris AM1 was investigated using p-nitroanilide (NA) derivatives of amino acids as substrates. PepN-like activity was decreased by inclusion of mixed whey proteins. While α-La did not have any effect on PepN-like activity, this activity was inhibited by β-Lg and BSA. In contrast, increased hydrolysis of Ala-Pro-pNA and Pro-pNA (specific substrates for PepX and Pepl, respectively) were observed on inclusion of whey proteins. Peptidase activity on Glu-pNA as substrate was not affected by the whey protein mixture, although it was decreased by α-La and increased by BSA. β-Lg did not have significant effect on PepA-like activity as assayed on Glu-pNA.