Silverman R B, Nandi D L
Department of Chemistry, Northwestern University, Evanston, Illinois 60208.
J Enzyme Inhib. 1990;3(4):289-94. doi: 10.3109/14756369009030377.
There is little difference in the extent of inactivation of beef liver microsomal vitamin K1 epoxide reductase by N-ethylmaleimide (NEM) whether or not the microsomes are pre-treated with dithiothreitol (DTT). The rat liver microsomal enzyme, however, is inactivated by NEM to a much greater extent if the microsomes are pre-treated with DTT. The beef liver enzyme activity is protected from NEM inactivation by the substrate, vitamin K1 epoxide. Ping-pong kinetics are exhibited by the beef liver enzyme. These results support a mechanism for vitamin K1 epoxide reductase in which the function of the required dithiol is to reduce an active site disulfide bond; however, the geometry of the active sites of the enzyme from rat and beef may be different.
无论肝微粒体是否用二硫苏糖醇（DTT）预处理，N - 乙基马来酰亚胺（NEM）对牛肝微粒体维生素K1环氧化物还原酶的失活程度几乎没有差异。然而，如果微粒体用DTT预处理，大鼠肝微粒体酶被NEM失活的程度要大得多。底物维生素K1环氧化物可保护牛肝酶活性不被NEM失活。牛肝酶表现出乒乓动力学。这些结果支持了维生素K1环氧化物还原酶的一种机制，其中所需二硫醇的功能是还原活性位点的二硫键；然而，大鼠和牛的酶活性位点的几何结构可能不同。
