An Active Kallikrein-α₂-Macroglobulin Complex Generated by Treatment of Human Plasma with Acetone

Abstract

Earlier functional studies on endogenous kinin formation in human plasma suggested that depending on the mode of treatment of the plasma, different kininogenases are activated predominantly: kininogenase I, activated by e.g. acid or acetone, acting on kininogen I; kininogenase II, activated by contact of plasma with glass, quartz etc., acting on kininogen II (Vogt, 1966). The existance of two kininogens, differing in molecular weight and affinity to plasma kallikrein, has meanwhile been well established. Kininogen II, highly sensitive to contact activated kininogenase(s), can be equated with high molecular weight kininogen (HMW-K), whereas kininogen I corresponds to low molecular weight kininogen (LMW-K) (Habal and Movat, 1972; Seidel, 1973; Habal et al., 1974). The existence of two kininogenases has been questioned however, since by fractionation of plasma other investigators found only one kinin-forming enzyme, plasma kallikrein — apart from the weakly active plasmin. Wendel et al. (1972) purified the contact-activated kininogenase (II) and found that it was not distinguishable in molecular size and isoelectric point from plasma kallikrein. The enzyme acted predominantly but not exclusively, on HMW-K (kininogen II). An attempt was therefore made to purify the acetone-activated enzyme (kininogenase I by the original definition) and to see whether it differs in its properties from the contact-activated enzyme.