Potential value of a rice protein extract, containing proteinaceous inhibitors against cysteine proteinases from Porphyromonas gingivalis, for managing periodontal diseases.

Arg-specific gingipain (Rgp) is a major pathogenic determinant of Porphyromonas gingivalis which is a major pathogen in periodontal disease. We prepared protein extracts with Rgp-inhibitory activity from polished rice (Oryza sativa) and evaluated the effects of these extracts on the growth and pathogenicity of P. gingivalis. The extracts inhibited the proteolytic degradation of human proteins by P. gingivalis proteinases, and repressed the growth and homotypic biofilm formation of P. gingivalis. The disruption of adhesion of epithelial cells by P. gingivalis was also restricted by the rice protein extracts. Our results suggested that the rice protein extracts suppressed the pathogenicity and growth of P. gingivalis by inhibiting the bacterial proteinase activities, implying that the Rgp-inhibitory proteins prepared from rice may be potentially valuable as nutraceutical agents for preventing periodontal diseases.