A non-essential glutamyl aminopeptidase is required for optimal growth of Lactococcus lactis MG1363 in milk.
Degenerate PCR primers were designed from the N-terminal amino acid sequence of a glutamyl aminopeptidase (PepA) from Lactococcus lactis. These primers were used to screen a lambda library for clones containing the gene (pepA) encoding PepA. The DNA sequence of a 2.1 kb fragment containing pepA was determined. The sequence revealed the presence of one complete and two incomplete open reading frames (ORFs). The complete ORF encodes a putative protein of 353 amino acids with a predicted N-terminal sequence identical to that determined for purified PepA. The pepA gene was subcloned on an Escherichia coli plasmid vector and production of active PepA was confirmed by means of a zymogram. Mutants of L. lactis in which the pepA gene was inactivated grew to normal cell densities in milk but exhibited a reduced growth rate during the exponential phase. Thus whilst PepA is required for optimal growth it is not essential.
Institute of Food Research, Norwich Laboratory, Colney, UK.
K J
KJ
l'Anson
S
S
Movahedi
H G
HG
Griffin
M J
MJ
Gasson
F
F
Mulholland
D000595:Amino Acid Sequence; D000626:Aminopeptidases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D002480:Cellulase / Q000235:genetics; D003001:Cloning, Molecular; D003013:Clostridium / Q000201:enzymology / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics; D015723:Gene Library; D043384:Glutamyl Aminopeptidase; D013294:Lactococcus lactis / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development*; D008892:Milk / Q000382:microbiology*; D008969:Molecular Sequence Data; D016296:Mutagenesis; D016366:Open Reading Frames; D017386:Sequence Homology, Amino Acid
D017931:DNA Primers; D004269:DNA, Bacterial; D002480:Cellulase; D000626:Aminopeptidases; D043384:Glutamyl Aminopeptidase