Action of plant proteinase inhibitors on enzymes of the kallikrein kinin system.

Serine proteinase inhibitors, in the seeds of several Leguminosae from the Pantanal region (West Brazil), were studied using bovine trypsin, Factor XIIa and human plasma kallikrein. The inhibitors were purified from Enterolobium contortisiliquum (Mr = 23,000), Torresea cearensis (Mr = 13,000), Bauhinia bauhinioides (Mr = 20,000), Bauhinia mollis (Mr = 20,000) and Bauhinia pentandra (Mr = 20,000). E. contortisiliquum inhibitor inactivates all three enzymes, whereas the T. cearensis inhibitor inactivates trypsin and Factor XIIa, but does not affect plasma kallikrein. B. bauhinioides and B. pentrandra inhibitors, on the other hand, inactivate trypsin and plasma kallikrein but only the B. pentandra inhibitor affects Factor XIIa, and B. mollis inhibitor causes trypsin inactivation only. Calculated Ki values were between 10(-7) and 10(-9) M. Chymotrypsin, like trypsin, is also inhibited, but with lower affinity. The trypsin inhibitors, isolated from E. contortisiliquum, B. pentandra, B. bauhinioides and B. mollis seem to be of the Kunitz type; the inhibitor purified from T. cearensis is of the Bowman-Birk type.