Activation of blood coagulation factor IX by gingipains R, arginine-specific cysteine proteinases from Porphyromonas gingivalis

The effect of two arginine-specific cysteine proteinases (gingipains R) fro m Porphyromonas gingivalis, an aetiological factor of adult periodontitis, on the activation of human factor IX was investigated in the presence of et hylene glycol, an activity enhancer of activated factor IX (factor IXa). wi th the use of a fluorogenic oligopeptide substrate. Each gingipain R rapidl y activated factor IX but the 95 kDa proteinase complex (HRgpA) that contai ns both haemagglutinin/adhesion and catalytic domains was 2.4-fold more eff icient than the single-chain 50 kDa gingipain R (RgpB), which has only a ca talytic domain. SDS/PAGE and N-terminal sequence analysis of factor IX dige stion fragments indicated that, like all endogenous activators, gingipains R also produce factor IXa beta via an IXa intermediate. Significantly, phos pholipids augmented the activation of factor IS by HRgpA but not by RgpB in a Ca2+-dependent manner. In the presence of both cofactors the kinetic eff iciency of HRgpA to activate factor IX (k(cat)/K-m = 1.9 x 10(6) M-1.s(-1)) was 8.5-fold higher than that Of RgpB (k(cat)/k(m) = 2.3 x 10(5) M-1.s(-1) ) and double that of the factor VIIa-tissue factor complex. but 8-fold lowe r than that for factor XIa. A comparison of the relative activation rates o f factor IX, factor X and prothrombin directly in plasma by HRgpA suggests a significant contribution for factor IX conversion in blood coagulation in duced by gingipains R. Taken together, gingipains R are the first-reported activators of factor IX of bacterial origin. By this effect they could be i nvolved in the production of thrombin as well as the subsequent generation of prostaglandins and interleukin 1, all of which have been found to be ass ociated with the development and progression of periodontitis.