Self Defence Mechanism of Porphyromonas gingivalis and Its Periodontopathogenicity

点击翻译按钮获取中文摘要

Porphyromonas gingivalis (P.g.) predominantly consumes arginine in the anaerobic BHI-broth, suggesting that this amino acid could be the primary energy source. Arginine carboxypeptidase, which is one of enzymes to participate in releasing arginine from peptides, was isolated and purified from cytoplasm of P.g. cells. SDS-PAGE of the enzyme with 2-mercaptoethanol revealed the presence of three major bands of 42, 33 and 32kDa, of which 30 amino acid sequences at NHィイD22ィエD2-terminal were identical, YEWNAYPTYEAYISMMEEFQT-KYPSLXTXS. The open reading frame (ORF), suspected from the nucleotide sequences corresponding to the N-terminal amino acids on the data bases containing unfinished P.g. W83 genome, showed to include zinc-binding regions signature, suggesting a zinc carboxypeptidase. In order to release arginine from the inside of the peptides, this enzyme, which was determined as a exo-type of carboxypeptidase, could work in combination with the trypsin like enzyme (cystein protease), which is considered as the main periodontopathogen of this bacterium. In relation to the arginine consumption and energy production, cell extracts of P. g. clearly demonstrated enzyme activities for the arginine deminase pathway and the adenosine triphosphate production. Besides arginine catabolism, P. g. conserved the heat-shock protein and increased the synthesis after a thermal shock, suggesting the physiologic role to protect their own cells. These results show that P. g. possesses self-defense systems by consuming periodontal tissues in the deep anaerobic pockets and producing heat-shock proteins for the changes of their environments.