Lysine- and arginine-specific proteinases from Porphyromonas gingivalis. Isolation, characterization, and evidence for the existence of complexes with hemagglutinins

Abstract

Porphyromonas gingivalis contains many virulence factors that have been implicated as participants in the progression of periodontal disease. It has been shown to produce proteinases of "trypsin-like" specificity in a number of molecular forms, but previous work in our laboratory resulted in the purification of a major arginine-specific cysteine proteinase, gingipain, which contradicted this supposed specificity. In this study, separate proteinases with arginine and lysine specificity were isolated from a high molecular mass fraction of the P. gingivalis culture fluid. The arginine-specific enzyme was found, by amino acid sequencing studies, to be a high molecular mass form of gingipain, formed by the 50-kDa gingipain noncovalently complexed with 44-kDa binding proteins, subsequently identified as hemagglutinins. The 60-kDa lysine-specific proteinase, referred to as Lys-gingipain, was also found to have one of these hemagglutinins complexed with it in the same manner. Lys-gingipain was found to be a cysteine proteinase with optimal activity and stability at pH 8.0-8.5 and was extensively characterized in terms of its specificity and activation characteristics. The proteinase-hemagglutinin complexes may be important in the uptake of hemin, a vital metabolite for P. gingivalis, via hemagglutination and subsequent hemolysis of erythrocytes.