Observations on Plasma Kinin Forming Enzymes
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Using various types of chromatography and electrophoresis, Kagen et al (1962) and Webster (1968) found in human serum one kallikrein, Eisen and Glanville (1969) two, and Colman et al (1969) three, of which two may have been a monomer and polymer of the same enzyme. Evidence for a kininogenase differing from the γ-globulin plasma kallikrein was also reported by Armstrong and Mills (1964). Plasma also appears to contain as many as four factors capable of activating the prekallikreins. It is not yet certain how many of these factors form part of a system comparable to the cascade sequence of blood clotting. Most authors present intrinsic plasma kinin formation as a sequence of three pre-enzyme — enzyme transformations. The first step (activation of factor XII) and the third step (activation of plasma kallikrein) are well established. The intermediate enzyme of the second stage may be an activator (PF/Dil.; Mason and Miles, 1962), or both an activator and kininogenase (‘kininogenase II’; Vogt, 1966). Evidence has also been reported that factor XII acts directly on the main kallikrein (Nagasawa et al., 1968), or even directly on kininogen (Rocha e Silva et al., 1967).
KeywordsHuman Plasma Heated Plasma Plasma Kallikrein Intermediate Enzyme Cascade Sequence
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