Characterization of Human Salivary Kallikrein: Reactivities to Human Plasma Kininogens and Proteinase Inhibitors

Abstract

In order to clarify the enzymatic properties of human salivary kallikrein, we investigated its actions on human plasma kininogens and response to proteinase inhibitors. Salivary kallikrein released kinin from both LMW and HMW kininogens, but acted preferentially on LMW kininogen. Salivary kallikrein did not completely release the kinin from HMW kininogen even after prolonged incubation (up to 60 min). The kinin releasing activity of salivary kallikrein was not inhibited by plasma proteinase inhibitors such as α₂M, α₂PI, AT III, and C1 INA after preincubation for 60min at 37°C, but was inhibited progressively by α₁AT as a function of prein-cubation time. SDS-PAGE revealed that concomitantly with the progressive inhibition a new band of 92, 000 daltons, which seemed to be a complex of salivary kallikrein and α₁AT, was produced. The kininogen-depleted plasma inhibited the salivary kallikrein to the same degree as α₁AT. Therefore, it is suggested that α₁AT is the only inhibitor of salivary kallikrein in human plasma.