Charged casein-derived oligopeptides competitively inhibit the transport of a reporter oligopeptide by Lactococcus lactis.
OBJECTIVE
To study the effect of casein-derived peptides, accumulated during growth of Lactococcus lactis in milk, on its oligopeptide transport (Opp) function.


RESULTS
This effect was estimated by analysing the ability of casein-derived peptides to compete for the transport of a reporter peptide by whole L. lactis cells. The transport of the reported peptide was monitored by determining the intracellular concentrations of the corresponding amino acids by means of reverse-phase high-performance liquid chromatography (HPLC). Uptake of the reporter peptide was competitively inhibited by casein-derived peptides. The competition was only because of charged casein-derived peptides, including anionic peptides. The design of specific pure peptides made it possible to evidence for a positive (or negative) influence exerted by the positively (or negatively) charged side chain of the N-terminal amino acid on the competition.


CONCLUSIONS
Charged casein-derived peptides impaired the oligopeptide transport function of L. lactis.


CONCLUSIONS
These results demonstrate an inhibition of Opp when too many peptides are produced by the proteinase. Peptide transport by Opp therefore represents a bottleneck for increasing the growth rate of L. lactis in milk.
Helinck
S
S
INRA-URLGA, Useful Bacterial Surface Proteins Group, 78352 Jouy-en-Josas Cedex, France.
Charbonnel
P
P
Foucaud-Scheunemann
C
C
Piard
J-C
JC
Juillard
V
V
D000818:Animals; D001426:Bacterial Proteins / Q000378:metabolism; D001431:Bacteriological Techniques / Q000379:methods; D001667:Binding, Competitive; D001692:Biological Transport; D002352:Carrier Proteins / Q000378:metabolism; D002364:Caseins / Q000378:metabolism*; D005516:Food Microbiology; D013294:Lactococcus lactis / Q000254:growth & development / Q000378:metabolism*; D008074:Lipoproteins / Q000378:metabolism; D008892:Milk / Q000382:microbiology*; D009842:Oligopeptides / Q000378:metabolism*
D001426:Bacterial Proteins; D002352:Carrier Proteins; D002364:Caseins; D008074:Lipoproteins; D009842:Oligopeptides; C046506:oligopeptide-binding protein, bacteria