Isolation and properties of a T-kininogenase from bovine erythrocyte membranes

A kininogenase from bovine erythrocyte membranes has been purified 140-fold by affinity chromatography on pepstatin A-Agarose followed by ion exchange chromatography on CM Cellulose. The purified enzyme showed an apparent molecular weight of 31,000 daltons as measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. ItspH optimum is 7.5, and it was totally inhibited by soybean trypsin inhibitor, phenylmethylsulfonylfluoride, aprotinin, pepstatin, and dithiotreitol, suggesting the presence of a disulfide bond(s) whose integrity is(are) essential for maintaining the native three-dimensional structure. The referred enzyme was able to release kinin from a substrate partially purified from rat plasma. The kininogenase was activated by Zn²⁺, Ca²⁺, and cysteine-HCl.