Infection and Immunity, February 2000, p. 716-724, Vol. 68, No. 2
0019-9567/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Department of Microbiology1 and Department of Pathology,3 Nippon Dental University, Fujimi 1-9-20, Chiyoda-ku, Tokyo 102-8159, and Scientific Instrument Center, Toyama Medical and Pharmaceutical University, Sugitani, Toyama 930-0152,2 Japan
Received 19 July 1999/Returned for modification 14 September 1999/Accepted 30 October 1999
Porphyromonas gingivalis is a major pathogen associated with adult periodontitis. We cloned and sequenced the gene (dpp) coding for dipeptidyl aminopeptidase IV (DPPIV) from P. gingivalis W83, based on the amino acid sequences of peptide fragments derived from purified DPPIV. An Escherichia coli strain overproducing P. gingivalis DPPIV was constructed. The enzymatic properties of recombinant DPPIV purified from the overproducer were similar to those of DPPIV isolated from P. gingivalis. The three amino acid residues Ser, Asp, and His, which are thought to form a catalytic triad in the C-terminal catalytic domain of eukaryotic DPPIV, are conserved in P. gingivalis DPPIV. When each of the corresponding residues of the enzyme was substituted with Ala by site-directed mutagenesis, DPPIV activity significantly decreased, suggesting that these three residues of P. gingivalis DPPIV are involved in the catalytic reaction. DPPIV-deficient mutants of P. gingivalis were constructed and subjected to animal experiments. Mice injected with the wild-type strain developed abscesses to a greater extent and died more frequently than those challenged with mutant strains. Mice injected with the mutants exhibited faster recovery from the infection, as assessed by weight gain and the rate of lesion healing. This decreased virulence of mutants compared with the parent strain suggests that DPPIV is a potential virulence factor of P. gingivalis and may play important roles in the pathogenesis of adult periodontitis induced by the organism.
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