CLONING AND ANALYSIS OF THE PEPV DIPEPTIDASE GENE OF LACTOCOCCUS-LACTIS MG1363

The gene pepV, encoding a dipeptidase from Lactococcus lactis subsp. c remoris MG1363, was identified in a genomic library in pUC19 in a pept idase-deficient Escherichia coli strain and subsequently sequenced. Pe pV of L. lactis is enzymatically active in E. coli and hydrolyzes a br oad range of dipeptides but no tri-, tetra-, or larger oligopeptides. Northern (RNA) and primer extension analyses indicate that pepV is a m onocistronic transcriptional unit starting 24 bases upstream of the AU G translational start codon. The dipeptidase oft. lactis was shown to be similar to the dipeptidase encoded by pepV of L. delbrueckii subsp. lactis, with 46% identity in the deduced amino acid sequences. A PepV -negative mutant of L. lactis was constructed by single-crossover reco mbination. Growth of the mutant strain in milk was significantly slowe r than that of the wild type, but the strains ultimately reached the s ame final cell densities.