The effect of tryptase from human mast cells on human prekallikrein

Tryptase, the dominant protease in human mast cells, was examined for its effect on human prekallikrein. Tryptase in the presence and absence of heparin failed to activate prekallikrein as shown in a spectrophotometric assay for kallikrein employing benzoy 1-pro-phe-arg-p-nitroanilide. Treated prekallikrein was converted to active kallikrein by bovine trypsin. Prekallikrein cleavage products were analyzed by electrophoresis in polyacrylamide gels under denaturing conditions (+/- reduction). Tryptase caused no apparent cleavage under conditions where trypsin caused complete cleavage. Thus, tryptase, which has previously been shown to lack kallikrein and kininase activities, neither activates nor destroys prekallikrein.