title: The occurrence of two intracellular oligoendopeptidases in Lactococcus lactis and their significance for peptide conversion in cheese.
abstract: Two intracellular oligopeptide-preferring endopeptidases have been detected in Lactococcus lactis. A neutral thermolysin-like oligoendopeptidase (NOP) has been purified to homogeneity and an alkaline oligoendopeptidase has been partially purified. The specificity of the oligoendopeptidases towards important intermediary cheese peptides, produced by chymosin action on the caseins, clearly differs from that of the cell-envelope proteinase (CEP). NOP is active under conditions prevailing in cheese and contributes to initial proteolysis in a young cheese. It probably plays a crucial role in the degradation of an important bitter peptide in cheese, the beta-casein 193-209 fragment. The relatively low activity of the alkaline endopeptidase is further suppressed in cheese by the highly competitive actions of NOP and CEP.
authors.affiliation: Department of Biophysical Chemistry, Netherlands Institute for Dairy Research (NIZO), Ede, The Netherlands.
authors.forename: R
authors.initials: R
authors.lastname: Baankreis
authors.forename: S
authors.initials: S
authors.lastname: van Schalkwijk
authors.forename: A C
authors.initials: AC
authors.lastname: Alting
authors.forename: F A
authors.initials: FA
authors.lastname: Exterkate
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000302:isolation & purification* / Q000378:metabolism; D002611:Cheese / Q000382:microbiology*; D002851:Chromatography, High Pressure Liquid; D010450:Endopeptidases / Q000302:isolation & purification* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000378:metabolism; D013294:Lactococcus lactis / Q000201:enzymology* / Q000235:genetics; D008894:Milk Proteins / Q000378:metabolism*; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism*; D013379:Substrate Specificity
chemical_list: D001426:Bacterial Proteins; D008894:Milk Proteins; D010455:Peptides; D010450:Endopeptidases