Article Abstract:
The cloning and sequencing of the gene encoding the aminopeptidase PepC from L. lactis subsp. cremoris AM2 is discussed. The genetic determinant encoding aminopeptidase PepC was cloned by complementation of the pepN gene from Eschirichia coli 1047. The clones were subjected to DNA sequence analysis and were searched for protein sequences showing homology to the deduced protein encoded by open reading frame. Results indicate an intracellular location of the enzyme as no signal sequence was found.
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Article Abstract:
The localization of five peptideaes in Lactococcus lactis was studied. These peptides, which include an endopeptidase, tripeptidase, an X-prolyl-dipetidyl aminopeptidase (XPDAP) and two aminopeptidase, were analysed by immunonoblotting after cell fractionation and by electron microscopy of immunogold-labeled peptidases. Results showed that all the peptidases are intracellular. However, peripheral location was also detected for the endopeptidase, the XPDAP, and the tripeptidase.
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Article Abstract:
Oligopeptides appear to be the primary nitrogen source for Lactococcus lactis growing in milk. The growth in milk of L. lactis strains with and without proteinase revealed that both appeared to use oligopeptides as opposed to free amino acids or di- and tripeptides. Strains deficient in oligopeptide transport had impaired growth in milk. The strains with proteinase exhibited a second growth phase that involved the hydrolysis of milk proteins to yield oligopeptides.
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