SUMMARY: In peptide uptake increases the internal concentration of amino acids and thus triggers amino acid secretion. The peptide uptake system is stimulated by a factor of two in cells grown on pure peptone medium in comparison to peptone media with additional carbon sources. Uptake depends on the proton-motive force and shows a broad substrate spectrum. Peptide uptake is characterized by a of about 230 μM and a of 12 nmol min (mg dry wt) for the peptide lysyl-alanine (Lys-Ala). Lysine secretion in the wild-type of does not show Michaelis-Menten-type kinetics as reported for the producing strains DG 52-5 and MH 20-22B. The secretion of lysine depends on the composition of the medium in which the cells were grown prior to the initiation of secretion by peptide uptake. The lack of secretion activity when the cells are shifted to peptone medium in the presence of chloramphenicol indicates that protein synthesis is necessary for this regulatory process.


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