Cytochrome P-450 of adrenal mitochondria. In vitro and in vivo changes in spin states.
Cytochrome P-450 of adrenal mitochondria. In vitro and in vivo changes in spin states.
复制标题
肾上腺线粒体的细胞色素 P-450。
DOI：
10.1016/s0021-9258(19)41353-7
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发表时间：
1975
期刊：
影响因子：
--
通讯作者：
W. Orme
中科院分区：
文献类型：
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作者：
C. Jefcoate;W. Orme
类固醇诱导的差异光谱已用于检查胆固醇与肾上腺线粒体细胞色素 P-450 的结合，后者参与胆固醇侧链裂解 (P-450scc) 以及酶系统周转导致的细胞色素中胆固醇的消耗。由 cholest-5-ene-3beta、25-二醇（25-羟基胆固醇）和 cholest-5-ene-3beta、20α、22R-三醇（20α、22R 二羟基胆固醇）诱导的 I 型差异光谱已用于定量胆固醇与细胞色素 P-450scc 上两个位点（I 和 II）的结合。体内促肾上腺皮质激素 (ACTH) 的作用以及钙离子或磷酸盐离子对分离线粒体的作用会刺激胆固醇与位点 I 结合，但不与位点 II 结合。然而，源自卵磷脂-胆固醇胶束的胆固醇与这两个位点结合。苹果酸诱导的胆固醇消耗的发生率与卵磷脂-胆固醇胶束中胆固醇的转移率相当。然而，即使在暴露于苹果酸10分钟后，胆固醇-细胞色素P-450scc复合物的残留比例仍然存在，并且在放线菌酮治疗和应激大鼠的线粒体中具有相似的量级。这表明这反映了胆固醇-细胞色素复合物的反应性较低的形式。类固醇诱导的差异光谱表明，在体外线粒体胆固醇代谢后和体内 ACTH 作用抑制后，细胞色素 P-450scc 上的位点 I 和 II 类似地被耗尽。去除细胞色素 P-450cc 处积累的胆固醇后，肾上腺细胞厌氧。当厌氧现象被阻止时，新分离的线粒体中的细胞色素 P-450scc 显然基本上不含复合胆固醇，无论 ACTH 作用的程度如何。将线粒体悬浮在 4 度的 0.25 M 蔗糖中 30 分钟后，胆固醇与细胞色素 P-450scc 结合。在对大鼠进行乙醚应激治疗期间，这一过程的程度不受放线菌酮存在的影响。结论是，至少有两个线粒体胆固醇库可以接触细胞色素 P-450scc，但 ACTH 仅刺激最容易与细胞色素相互作用的库。
Steroid-induced difference spectra have been used to examine the combination of cholesterol with adrenal mitochondrial cytochrome P-450 which participates in cholesterol side chain cleavage (P-450scc) and the depletion of cholesterol from the cytochrome which results from turnover of the enzyme system. Type I difference spectra-induced by cholest-5-ene-3beta, 25-diol (25-hydroxycholesterol) and cholest-5-ene-3beta, 20 alpha, 22R-triol (20alpha, 22R dihydroxycholesterol) have been used to quantitate binding of cholesterol to two sites (I and II) on cytochrome P-450scc. The action of adrenocorticotropic hormone (ACTH) in vivo and the action of calcium or phosphate ions on isolated mitochondria stimulate the combination of cholesterol with site I but not site II. Cholesterol derived from lecithin-cholesterol micelles, however, binds to both sites. Malate-induced cholesterol depletion occurred at a comparable rate to the transfer of cholesterol from lecithin-cholesterol micelles. However, a residual proportion of cholesterol-cytochrome P-450scc complexes remained, even after 10 min of exposure to malate, and was of similar magnitude in mitochondria from both cycloheximide-treated and stressed rats. It is suggested that this reflects a less reactive form of cholesterol-cytochrome complex. Steroid-induced difference spectra indicate that sites I and II on cytochrome P-450scc are similarly depleted after metabolism of mitochondrial cholesterol in vitro and after inhibition of the action of ACTH in vivo. Anaerobiosis of adrenal cells after excision of the accumulation of cholesterol at cytochrome P-450cc. When anaerobiosis was prevented, cytochrome P-450scc in the freshly isolated mitochondria was apparently essentially free of complexed cholesterol, irrespective of the extent of ACTH action. For 30 min after suspension of the mitochondria in 0.25 M sucrose at 4 degrees, cholesterol combines with cytochrome P-450scc. The extent of this process was not affected by the presence of cycloheximide during ether stress treatment of the rats. It is concluded that there are at least two pools of mitochondrial cholesterol with access to cytochrome P-450scc but that ACTH stimulates only the pool which most readily interacts with the cytochrome.