The opdB locus encodes the trypsin-like peptidase activity of Treponema denticola

High levels of Treponema denticola in subgingival dental plaque are associa ted with severe periodontal disease. T. denticola, along with Porphyromonas gingivalis and Bacteroides forsythus, are the only cultivatable oral micro organisms that produce significant amounts of "trypsin-like" peptidase acti vity. The ability of subgingival plaque to hydrolyze N-alpha -benzoyl-DL-ar ginine-2-naphthylamide (BANA) is associated with high levels of one or more of these organisms. The purpose of this study was to identify the gene enc oding trypsin-like activity in T. denticola and thus facilitate molecular-l evel studies of its potential role in disease. Using published peptide sequ ences of a T. denticola surface-associated oligopeptidase with BANA-hydroly zing activity, we identified the gene, designated opdB, in an apparently no ncoding region of the T. denticola genome unannotated contigs (11/2000; htt p://www.tigr.org). The opdB gene begins with a TTG start codon and encodes a 685-residue peptide with high homology to the oligopeptidase B family in prokaryotes and eukaryotes. An isogenic T. denticola opdB mutant was constr ucted by allelic. replacement mutagenesis using an ermF/AM gene cassette. T he mutant lacked BANA-hydrolyzing activity and had a slightly slower growth rate than the parent strain. This mutant will be used in future studies of interactions of T. denticola with host cells and tissue.