Marcum J A, Kline D L
Comp Biochem Physiol B. 1983;75(3):389-94. doi: 10.1016/0305-0491(83)90345-0.
Streptokinase, a bacterial protein, forms a complex with human plasminogen which results in a conformational change in the plasminogen molecule and the exposure of an active center. The plasminogen-streptokinase complex is an activator of plasminogen and is rapidly converted to a plasmin-streptokinase complex which, in the human, is also an activator of plasminogen. Species differences have been found in the reaction of streptokinase with plasminogen varying from no active complex formation at one extreme to the rapid formation of an active activator complex at the other, with resultant differences in rates of complex formation and the yield of plasmin. Explanation of these species differences at a molecular level are discussed as well as the possible application of complex formation in a variety of biological systems as a mechanism to produce variation in enzyme activities in proportion to the concentration of substrate available.
链激酶是一种细菌蛋白，它与人纤溶酶原形成复合物，导致纤溶酶原分子发生构象变化并暴露出活性中心。纤溶酶原 - 链激酶复合物是纤溶酶原的激活剂，并迅速转化为纤溶酶 - 链激酶复合物，在人体内，该复合物也是纤溶酶原的激活剂。已发现链激酶与纤溶酶原的反应存在物种差异，从一端的无活性复合物形成到另一端的活性激活剂复合物的快速形成，结果是复合物形成速率和纤溶酶产量存在差异。本文讨论了这些物种差异在分子水平上的解释，以及复合物形成在各种生物系统中作为一种机制的可能应用，该机制可使酶活性根据可用底物浓度产生变化。
