Boutaud O, Dolis D, Schuber F
Laboratoire de Chimie Bioorganique (CNRS URA-1386), Faculté de Pharmacie, Illkirch, France.
Biochem Biophys Res Commun. 1992 Oct 30;188(2):898-904. doi: 10.1016/0006-291x(92)91140-l.
Kinetic studies on the cyclization of 2,3(S)-oxido and 2,3(S):22(S),23-dioxido[14C]squalene catalyzed by liver oxidosqualene-lanosterol cyclase revealed a specificity (in terms of V/Km) of the enzyme for the diepoxide. The specificity ratio was dependent on the enzyme preparation, i.e. purified or microsomal, and was highest (about 5) with the microsomal enzyme in the presence of supernatant protein factors. These results explain why, in the presence of cyclase inhibitors, the squalene epoxides can be channeled into a cholesterol biosynthesis regulatory pathway via 24(S),25-epoxylanosterol and 24(S),25-epoxycholesterol.
对肝氧化角鲨烯-羊毛甾醇环化酶催化的2,3(S)-环氧和2,3(S):22(S),23-二环氧[14C]角鲨烯环化的动力学研究表明，该酶对二环氧物具有特异性（以V/Km计）。特异性比率取决于酶制剂，即纯化的或微粒体的，并且在存在上清蛋白因子的情况下，微粒体酶的特异性比率最高（约为5）。这些结果解释了为什么在存在环化酶抑制剂的情况下，角鲨烯环氧化物可以通过24(S),25-环氧羊毛甾醇和24(S),25-环氧胆固醇进入胆固醇生物合成调节途径。
