Arginine Catabolism and Its Role in Pathogenecity by Periodontopathogenic Bacteria

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Porphyromonas gingivalis predominantly consumes arginine in the culture medium, suggesting that this amino acid could be the energy source. In relation to the arginine comsuption, cell extracts of P.gingivalis clearly demonstrated enzyme activities for the arginine deiminase pathway and adenosine triphosphate production. The pathogenic properties of this bacterium have been studied extensively in relation to the proteolytic enzyme, especially a trypsin-like enzyme, which splits the bond at the carboxyl side of arginine containing peptide. To obtain free arginine from protein and /or peptide, we performed to elucidate presence and role the arginine carboxypeptidase which cleaves peptide bond at the amino side of arginine. Arginine carboxypeptidase was found in the culture medium and cells. The enzyme was isolated and purified from cytoplasm of P.gingivalis cells. SDS-PAGE of the enzyme revealed the presence of three major bands of 42, 33, and 32kDa, of which 30 amino acid sequences at NH_2-terminal were identical. The ORF, suspected from the nucleotide sequences corresponding to the N-terminal amino acids on the date bases containing unfinished P.gingivalis W83 genome, showed to include signature, suggesting a zinc carboxypeptidase. By Western blotting and immunomicroscopy, the enzyme was found to distribute widely in the cytoplasm and on the surface of the outer membrane of P.gingivalis cells. These results show that this enzyme may function to release arginine in collaboration with a trypsin-like enzyme, to obtain arginine from periodontal tissues in the deep anaerobic pockets during the growth of P.gingivalis. Consequently, these processes might result in the pathogenecity of this bacterium.