INTERACTION OF A TRYPSIN-LIKE-ENZYME OF PORPHYROMONAS-GINGIVALIS W83 WITH ANTITHROMBIN-III

We have previously observed that trypsin-like activity in' Porphyromonas gingivalis culture supernatants is inhibitable by the plasma arg-serpin antithrombin III (ATIII). This report demonstrates that a partially purified P. gingivalis trypsin-like enzyme (M(r) 47000) is inhibited by ATIII with an association rate constant (k(ass)) of 5.65 x 10(4) M-1 s-1 but does not form SDS-stable complexes. Heparin enhances the k(ass) and stabilizes the complexes but in either case such inhibition is temporary and results in ATIII inactivation by reactive centre proteolysis between R393-S394 . In the absence of heparin this is accompanied by N-terminal cleavage between K-39-I-40.