title: Classification of Lactococcus lactis cell envelope proteinase based on gene sequencing, peptides formed after hydrolysis of milk, and computer modeling.
abstract: Lactococcus lactis strains depend on a proteolytic system for growth in milk to release essential AA from casein. The cleavage specificities of the cell envelope proteinase (CEP) can vary between strains and environments and whether the enzyme is released or bound to the cell wall. Thirty-eight Lc. lactis strains were grouped according to their CEP AA sequences and according to identified peptides after hydrolysis of milk. Finally, AA positions in the substrate binding region were suggested by the use of a new CEP template based on Streptococcus C5a CEP. Aligning the CEP AA sequences of 38 strains of Lc. lactis showed that 21 strains, which were previously classified as group d, could be subdivided into 3 groups. Independently, similar subgroupings were found based on comparison of the Lc. lactis CEP AA sequences and based on normalized quantity of identified peptides released from αS1-casein and β-casein. A model structure of Lc. lactis CEP based on the crystal structure of Streptococcus C5a CEP was used to investigate the AA positions in the substrate-binding region. New AA positions were suggested, which could be relevant for the cleavage specificity of CEP; however, these could only explain 2 out of 3 found subgroups. The third subgroup could be explained by 1 to 5 AA positions located opposite the substrate binding region.
authors.affiliation: Department of Food Science, Faculty of Science, University of Copenhagen, Rolighedsvej 28, 1958 Frederiksberg, Denmark; Chr. Hansen A/S, 2970 Hørsholm, Denmark. Electronic address: dkmew@chr-hansen.com.
authors.forename: M W
authors.initials: MW
authors.lastname: Børsting
authors.affiliation: Chr. Hansen A/S, 2970 Hørsholm, Denmark.
authors.forename: K B
authors.initials: KB
authors.lastname: Qvist
authors.affiliation: Chr. Hansen A/S, 2970 Hørsholm, Denmark.
authors.forename: E
authors.initials: E
authors.lastname: Brockmann
authors.affiliation: Chr. Hansen A/S, 2970 Hørsholm, Denmark.
authors.forename: J
authors.initials: J
authors.lastname: Vindeløv
authors.affiliation: Chr. Hansen A/S, 2970 Hørsholm, Denmark.
authors.forename: T L
authors.initials: TL
authors.lastname: Pedersen
authors.affiliation: Department of Food Science, Faculty of Science, University of Copenhagen, Rolighedsvej 28, 1958 Frederiksberg, Denmark.
authors.forename: F K
authors.initials: FK
authors.lastname: Vogensen
authors.affiliation: Department of Food Science, Faculty of Science, University of Copenhagen, Rolighedsvej 28, 1958 Frederiksberg, Denmark.
authors.forename: Y
authors.initials: Y
authors.lastname: Ardö
mesh_terms: D018829:Adhesins, Bacterial; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002364:Caseins / Q000378:metabolism; D002462:Cell Membrane / Q000201:enzymology; D002473:Cell Wall / Q000201:enzymology; D003198:Computer Simulation; D010450:Endopeptidases; D006868:Hydrolysis; D013294:Lactococcus lactis / Q000201:enzymology*; D008892:Milk / Q000737:chemistry / Q000378:metabolism*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000378:metabolism; D012697:Serine Endopeptidases / Q000737:chemistry / Q000145:classification* / Q000235:genetics*; D013291:Streptococcus / Q000201:enzymology
chemical_list: D018829:Adhesins, Bacterial; D002364:Caseins; D010446:Peptide Fragments; D010455:Peptides; D010450:Endopeptidases; D012697:Serine Endopeptidases; C085783:lactocepin; C053088:C5a peptidase
keywords: Lactococcus lactis ssp. classification; cell envelope proteinase (CEP); computer modeling; substrate binding