Identification of Dipeptidyl-Peptidase (DPP)5 and DPP7 in Porphyromonas endodontalis, Distinct from Those in Porphyromonas gingivalis

Dipeptidyl peptidases (DPPs) that liberate dipeptides from the N-terminal end of oligopeptides are crucial for the growth of Porphyromonas species, anaerobic asaccharolytic gram negative rods that utilize amino acids as energy sources. Porphyromonas endodontalis is a causative agent of periapical lesions with acute symptoms and Asp/Glu-specific DPP11 has been solely characterized in this organism. In this study, we identified and characterized two P. endodontalis DPPs, DPP5 and DPP7. Cell-associated DPP activity toward Lys-Ala-4-methylcoumaryl-7- amide (MCA) was prominent in P. endodontalis ATCC 35406 as compared with the Porphyromonas gingivalis strains ATCC 33277, 16-1, HW24D1, ATCC 49417, W83, W50, and HNA99. The level of hydrolysis of Leu-Asp-MCA by DPP11, Gly- Pro-MCA by DPP4, and Met-Leu-MCA was also higher than in the P. gingivalis strains. MER236725 and MER278904 are P. endodontalis proteins belong to the S9- and S46-family peptidases, respectively. Recombinant MER236725 exhibited enzymatic properties including substrate specificity, and salt- and pH-dependence similar to P. gingivalis DPP5 belonging to the S9 family. However, the kcat/Km figure (194 mM21?sec21) for the most potent substrate (Lys-Ala-MCA) was 18.4-fold higher as compared to the P. gingivalis entity (10.5 mM21?sec21). In addition, P. endodontalis DPP5 mRNA and protein contents were increased several fold as compared with those in P. gingivalis. Recombinant MER278904 preferentially hydrolyzed Met-Leu-MCA and exhibited a substrate specificity similar to P. gingivalis DPP7 belonging to the S46 family. In accord with the deduced molecular mass of 818 amino acids, a 105-kDa band was immunologically detected, indicating that P. endodontalis DPP7 is an exceptionally large molecule in the DPP7/DPP11/S46 peptidase family. The enhancement of four DPP activities was conclusively demonstrated in P. endodontalis, and remarkable Lys-Ala-MCAhydrolysis was achieved by qualitative and quantitative potentiation of the DPP5 molecule

Pathogenicity of Vibrio splendidus strains associated with turbot larvae, Scophthalmus maximus

International audienceTurbot larvae were challenged with eight strains of Vibrio splendidus isolated from diseased larvae, plus a ninth strain pathogenic to scallop larvae (A515; Nicolas et al. 1996). Six strains caused heavy mortality but the scallop pathogen and the other two strains did not. All the strains shared a large number of phenotypic traits, and an attempt was made to relate virulence to genotype and phenotype. Five of the six pathogenic strains were very similar, as shown by RAPD fingerprinting and phenotypic characteristics. The relatedness of the other strains was intermediate between the main pathogenic group and V. splendidus ATCC 33125, but the DNA-DNA homology between the pathogenic group and the reference strain was still high (78% of reassociation rate). The non-pathogenic isolates may be a useful tool for determining the possible virulence factors, as all the isolates differed by few characteristics