Characterization of human salivary kallikrein: reactivities to human plasma kininogens and proteinase inhibitors.

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 alpha 2M, alpha 2PI, AT III, and C1 INA after preincubation for 60 min at 37 degrees C, but was inhibited progressively by alpha 1AT as a function of preincubation 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 alpha 1AT, was produced. The kininogen-depleted plasma inhibited the salivary kallikrein to the same degree as alpha 1AT. Therefore, it is suggested that alpha 1AT is the only inhibitor of salivary kallikrein in human plasma.