DEGRADATION AND DEBITTERING OF A TRYPTIC DIGEST FROM BETA-CASEIN BY AMINOPEPTIDASE-N FROM LACTOCOCCUS-LACTIS SUBSP CREMORIS WG2

The mode of action of purified aminopeptidase N from Lactococcus lacti s subsp. cremoris Wg2 on a complex peptide mixture of a tryptic digest from bovine beta-casein was analyzed. The oligopeptides produced in t he tryptic digest before and after aminopeptidase N treatment were ide ntified by analysis of the N- and C-terminal amino acid sequences and amino acid compositions of the isolated peptides and by on-line liquid chromatography-mass spectrometry. Incubation of purified peptides wit h aminopeptidase N resulted in complete hydrolysis of many peptides, w hile others were only partially hydrolyzed or not hydrolyzed. The tryp tic digest of beta-casein exhibits a strong bitter taste, which corres ponds to the strong hydrophobicity of several peptides in the tryptic digest of beta-casein. The degradation of the ''bitter'' tryptic diges t by aminopeptidase N resulted in a decrease of hydrophobic peptides a nd a drastic decrease of bitterness of the reaction mixture.