Gingipain aminopeptidase activities in Porphyromonas gingivalis

Bestatin, a specific inhibitor of metalloaminopeptidases,inhibits the growth of Porphyromonas gingivalis. To identify its target enzyme, a library of fluorescent substrates was used but no metalloaminopeptidase activity was found. The aminopeptidase activity of P. gingivalis was bestatin-insensitive and directed exclusively toward N-terminal arginine and lysine substrates. Class-specific inhibitors and gingipain-null mutants showed that gingipains were the only enzymes responsible for this activity.The kinetic constants obtained for Rgps were comparable to those of human aminopeptidases but Kgp aminopeptidase activity was weaker. This finding reveals a new role for gingipains as aminopeptidases in the degradation of proteins and peptides in P. gingivalis.