Isolation of a cationic fragment of high molecular mass kininogen and effect of this fragment on human plasma kallikrein activity.

The effect of a cationic fragment of high molecular mass (HMM) kininogen on kallikrein activity and the autocatalytic process of prekallikrein-to-kallikrein conversion were studied. Prekallikrein and kallikrein were obtained by ion exchange and affinity chromatography; the purification of HMM kininogen was achieved using QAE- and DEAE-Sephadex, and separation of the cationic fragment was carried out by gel filtration. It was shown that the fragment of HMM kininogen (mol. mass. 7000, high lysine content) suppressed the activity of a labile form of kallikrein and prevented activation of prekallikrein. A model of the prekallikrein-kallikrein system is proposed. The model is based on the recently established fact of occurrence of two kallikreins and two kallikrein precursors. It involves formation from kininogen, besides kinins, of a kallikrein inhibitor.