Purification, characterisation, cloning and sequencing of the gene encoding oligopeptidase PepO from Streptococcus thermophilus A

The oligopeptidase PepO From Sar Streptococcus thermophilus A was purified to protein homogeneity by a live-step chromatography procedure. It was esti mated to be a serine metallopeptidase of 70 kDa, with maximal activity at p H 6.5 and 41 degrees C. PepO has endopeptidase activity on oligopeptides co mposed of between five and 30 amino acids. PepO was demonstrated to be acti ve and stable at the pH. temperature and salt concentrations found in Swiss -type cheese during ripening. Using a battery of PCR techniques, the pepO g ene was amplified. subcloned and sequenced, revealing an open leading frame of 1893 nucleotides. The amino acid sequence analysis of the pepO gene-tra nslation product shows homology with PepO enzymes from other lactic acid ba cteria and contains the signature sequence of the metallopeptidase family. (C) 2000 Federation of European Microbiological Societies. Published by Els evier Science B.V. All rights reserved.