Specificity of a cell-envelope-located proteinase (PIII-type) from Lactococcus lactis subsp. cremoris AM1 in its action on bovine beta-casein.
The action of the cell-envelope proteinase (PIII-type) from Lactococcus lactis ssp. cremoris AM1 on bovine beta-casein was studied. The results were compared with those obtained earlier with (PI-type) proteinases from the cell envelope of other L. lactis strains. From a 4-h digest (pH 6.2; 15 degrees C) of beta-casein made with the PIII-type proteinase, 24 peptides were isolated and purified by selective precipitation followed by semi-preparative reversed-phase HPLC. Altogether, these peptides accounted for the preferential splitting of 16 peptide bonds in beta-casein by the PIII-type proteinase. In nine cases the primary cleavage site (P1-P'1) was a Glx-X or X-Glx peptide bond. In ten cases at least one large hydrophobic residue (Met, Leu, Tyr, Phe) formed part of the cleavable bond. The P2-P3 and/or P'2-P'3 regions of the substrate consisted of hydrophobic and/or negatively charged side chains or of side chains potentially involved in hydrogen bonds. Nine of the peptide bonds split were reported previously to be also susceptible to cleavage by PI-type proteinases, although the kinetics may be different. The PIII-type proteinase shows a broader specificity in its initial cleavage of beta-casein than does the PI-type.
Department of Biophysical Chemistry, Netherlands Institute for Dairy Research (NIZO), Ede.
S
S
Visser
A J
AJ
Robben
C J
CJ
Slangen
D000595:Amino Acid Sequence; D000818:Animals; D002364:Caseins / Q000737:chemistry* / Q000187:drug effects; D002417:Cattle; D002473:Cell Wall / Q000201:enzymology; D003546:Cysteine Endopeptidases / Q000737:chemistry* / Q000494:pharmacology; D006868:Hydrolysis; D013294:Lactococcus lactis / Q000201:enzymology*; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D013379:Substrate Specificity
D002364:Caseins; D010446:Peptide Fragments; D003546:Cysteine Endopeptidases; C042477:streptopain