CHOLESTEROL METABOLISM AND MITOCHONDRIAL CYTOCHROME P450

电子转移蛋白肾上腺素(ADX)与游离细胞色素P450结合 (Kd等于0.5微米)，但结合极大地激活了存在 胆固醇(kd等于0.02微米)。黄素蛋白ADX-还原酶结合ADX 亲和力更高，但这三种蛋白质的三元复合体不能 形式。胆固醇侧链断裂动力学表明阿昔洛韦“穿梭” ADX-还原酶与P450 SCC之间的关系。反应是通过离子的增加而激活的 强度，但被钙离子抑制(ID50等于50微米)。11. β-羟基化也利用ADX-穿梭，并通过增加 离子强度，但在这种情况下，钙离子是一种有效的激活剂。盐可能会 通过增强抑制物的解离来激活侧链切割 氧化阿昔洛韦，而对于11β-羟基化，盐效应完全是由于 将氧化ADX的稳态水平降至最低。已经开发出一种方法来处理 溶解肾上腺线粒体，分离内外膜，而 最大限度地减少胆固醇在膜之间的重新分配。氨基谷氨酰亚胺， 注射到应激大鼠体内，导致体内胆固醇增加 膜通过直接与P450scc结合。环己亚胺增强型总制剂 线粒体胆固醇和外膜水平升高。它是 结论是肾上腺ACTH激活的一个限速事件是转移 胆固醇从外线粒体膜到内膜 这一步骤与蛋白质合成有关。

The electron-transfer protein adrenodoxin (ADX) binds to free cytochrome P450 (Kd equals 0.5 microns), but binding is greatly activated by the presence of cholesterol (kd equals 0.02 microns). The flavoprotein ADX-reductase binds ADX with even higher affinity, but a ternary complex of all three proteins does not form. Kinetics of cholesterol side chain cleavage indicate that ADX "shuttles" between ADX-reductase and P450 scc. Reaction is activated by increased by ionic strength but is inhibited by Ca ions (ID50 equals 50 microns). 11 beta-hydroxylation also utilizes an ADX-shuttle and is activated by increased ionic strength but in this case Ca ions is a potent activator. Salt may activate side-chain cleavage by enhancing the dissociation of inhibitory oxidized ADX, while for 11 beta-hydroxylation the salt effect is due solely to minimizing steady-state levels of oxidized ADX. A method has been developed for lysing adrenal mitochondria and separating inner and outer membranes, while minimizing cholesterol redistribution between the membranes. Aminoglutethimide, injected into stressed rats, effected an increase in cholesterol in the inner membrane via direct binding to P450scc. Cycloheximde enhanced total mitochondrial cholesterol and enhancing levels in the outer membrane. It is concluded that a rate-limiting event in ACTH-activation of adrenals is transfer of cholesterol from the outer mitochondrial membrane to the inner membrane and that this step is coupled to protein synthesis.