Taylor F R, Saucier S E, Shown E P, Parish E J, Kandutsch A A
J Biol Chem. 1984 Oct 25;259(20):12382-7.
Support for the role of a cytosolic oxysterol-binding protein in the regulation of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase was obtained by correlating the relative binding affinities of a wide range of oxysterols to their potency in suppressing HMG-CoA reductase activity in mouse fibroblast cell cultures. Forty-seven oxysterols encompassing a 100-fold range of activity in both assays were tested and the two parameters were closely correlated for 35 of the sterols. Twelve sterols showed poor binding when compared to their ability to suppress HMG-CoA reductase activity in cell cultures. Among these were seven sterols with a ketone function at C-3. For this group, the discrepancy could be explained by their rapid conversion within cells to the 3 beta-hydroxy derivatives which have a much higher affinity for the binding protein. One sterol with 3-keto-4-ene grouping was not reduced to its 3 beta-hydroxy derivative in cells and thereby showed no discrepancy in the two assays. The remaining five sterols exhibiting discordant activities in the two tests contained 4,4-dimethyl moieties and were relatively weak suppressors of HMG-CoA reductase activity. Cellular metabolism of these sterols was not detected. Possible reasons for their apparent inactivity in the binding assay are discussed.
通过将多种氧化甾醇的相对结合亲和力与其在小鼠成纤维细胞培养物中抑制3-羟基-3-甲基戊二酰辅酶A（HMG-CoA）还原酶活性的效力相关联，获得了对胞质氧化甾醇结合蛋白在调节HMG-CoA还原酶中作用的支持。测试了47种氧化甾醇，它们在两种测定中的活性范围达100倍，其中35种甾醇的这两个参数密切相关。与它们在细胞培养物中抑制HMG-CoA还原酶活性的能力相比，12种甾醇显示出较差的结合能力。其中有7种在C-3位具有酮功能的甾醇。对于该组，差异可以通过它们在细胞内快速转化为对结合蛋白具有更高亲和力的3β-羟基衍生物来解释。一种具有3-酮-4-烯基团的甾醇在细胞中未还原为其3β-羟基衍生物，因此在两种测定中均未显示差异。在两项测试中表现出不一致活性的其余5种甾醇含有4,4-二甲基部分，并且是HMG-CoA还原酶活性的相对较弱的抑制剂。未检测到这些甾醇的细胞代谢。讨论了它们在结合测定中明显无活性的可能原因。
