Thomassin J, Dragacci S, Faye B, Magdalou J, Siest G
Comp Biochem Physiol C Comp Pharmacol Toxicol. 1986;83(1):127-31. doi: 10.1016/0742-8413(86)90024-1.
After induction by phenobarbital and 3-methylcholanthrene, UDP-glucuronosyltransferase involved mainly in the conjugation of planar substrates was purified. Compared to the microsomal enzyme, the purified protein exhibited less affinity towards the substrates, but the corresponding Vmaxs were increased. These results were attributed to a change in the lipid environment of the purified enzyme. The conjugation rate for 4-hydroxycoumarine was 15-45 times less than that measured for the 7-hydroxyisomer with the microsomal or the purified enzymes. Immunoprecipitation studies of the enzyme revealed that the two compounds were transformed by the same enzyme, or metabolized by two separate enzymes presenting the same antigenic site. The orientation of the hydroxyl group of planar aglycones in the active site is the determinant for the efficiency of catalysis.
经苯巴比妥和3-甲基胆蒽诱导后，主要参与平面底物结合反应的UDP-葡萄糖醛酸基转移酶被纯化。与微粒体酶相比，纯化后的蛋白质对底物的亲和力较低，但相应的最大反应速度（Vmax）有所增加。这些结果归因于纯化酶脂质环境的变化。4-羟基香豆素的结合率比用微粒体酶或纯化酶测得的7-羟基异构体的结合率低15至45倍。对该酶的免疫沉淀研究表明，这两种化合物由同一种酶转化，或由具有相同抗原位点的两种不同酶代谢。平面苷元羟基在活性位点的方向是催化效率的决定因素。
