title: Relationship between utilization of proline and proline-containing peptides and growth of Lactococcus lactis.
abstract: Proline, which is the most abundant residue in beta-casein, stimulates growth of Lactococcus lactis in a proline-requiring strain (Lactococcus lactis subsp. cremoris Wg2) and in a proline-prototrophic strain (Lactococcus lactis subsp. lactis ML3). Both strains lack a proline-specific uptake system, and free proline can enter the cell only by passive diffusion across the cytoplasmic membrane. On the other hand, lactococci can actively take up proline-containing peptides via the lactococcal di- and tripeptide transport system, and these peptides are the major source of proline. Consequently, lactococcal growth on amino acid-based media is highly stimulated by the addition of proline-containing di- and tripeptides. Growth of L. lactis subsp. lactis ML3 on chemically defined media supplemented with casein does not appear proline limited. Addition of dipeptides (including proline-containing peptides) severely inhibits growth on a casein-containing medium, which indicates that the specific growth rate is determined by the balanced supply of different di- or tripeptides which compete for the same di- and tripeptide transport system.
authors.affiliation: Department of Microbiology, University of Groningen, Haren, The Netherlands.
authors.forename: E J
authors.initials: EJ
authors.lastname: Smid
authors.forename: W N
authors.initials: WN
authors.lastname: Konings
mesh_terms: D000595:Amino Acid Sequence; D001692:Biological Transport; D004151:Dipeptides / Q000378:metabolism; D007700:Kinetics; D013294:Lactococcus lactis / Q000254:growth & development* / Q000378:metabolism; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism*; D011392:Proline / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D004151:Dipeptides; D009842:Oligopeptides; D011392:Proline