Mutant forms of cytochrome P-450 controlling both 18- and 11beta-steroid hydroxylation in the rat.
Mutant forms of cytochrome P-450 controlling both 18- and 11beta-steroid hydroxylation in the rat.
复制标题
细胞色素 P-450 的突变形式控制大鼠体内 18- 和 11β-类固醇羟基化。
DOI：
10.1021/bi00651a010
复制
发表时间：
1976
期刊：
影响因子：
2.9
通讯作者：
L. Dahl
中科院分区：
文献类型：
--
作者：
J. Rapp;L. Dahl
先前显示，盐敏感（S）和盐抗性（R）品系大鼠中类固醇18-和11 β-羟化酶活性之间的相互关系受具有两个等位基因的单个遗传基因座控制，并且通过共显性遗传（Rapp，J. P.，和Dahl，L. K.（1972），Endocrinology 90，1435）。菌株特定的类固醇生成模式，其特征在于18-和11 β-羟化酶活性的相对大小，被认为是由肾上腺线粒体细胞色素P-450颗粒。在这些菌株中，一氧化碳对脱氧皮质酮的18-和11 β-羟基化的抑制表明，引起50%抑制的CO/O2比（即，同一菌株内18-和11 β-羟基化的瓦尔堡分配常数K）相同，但菌株间18-和11 β-羟基化的分配常数不同。（K值为：S大鼠，18-羟基化= 11.4 +/- 1.4; S大鼠，11 β-羟基化= 11.0 +/- 1.2; R大鼠，18-羟基化= 56.4 +/- 13.7; R大鼠，11 β-羟基化= 46.7 +/- 11.7）。这种菌株间差异对于18-和11 β-羟基化是独特的;即，在胆固醇侧链裂解或21-羟基化中未观察到。此外，18-和11 β-羟化酶的菌株特异性K值和菌株特异性类固醇生成模式，由于18-和11 β-羟化酶活性的相对大小分离在一起的F2群体。这些数据有力地表明，相同的细胞色素P-450参与18-和11 β-羟基化，并且这种细胞色素在S和R大鼠之间发生突变。反应皮质酮导致18-羟基皮质酮的K值是不同的S和R菌株之间，这表明突变细胞色素也参与了这种羟基化，但K值的转换皮质酮导致醛固酮菌株之间没有差异。这被解释为意味着皮质酮导致18-羟基皮质酮导致醛固酮的序列中的每一步都是由不同的细胞色素介导的，第二步的K值较低并且主导整个反应。推测第二步可能是在18位的第二次羟基化，产生18，18-二羟基皮质酮，其可能不稳定并分解成醛固酮和水。
A reciprocal relationship between steroid 18- and 11beta-hydroxylase activities in the salt susceptible (S) and the salt resistant (R) strains of rats was previously shown to be controlled by a single genetic locus with two alleles and inheritance by co-dominance (Rapp, J. P., and Dahl, L. K. (1972), Endocrinology 90, 1435). The strain specific steroidogenic patterns, characterized by the relative magnitudes of 18- and 11beta-hydroxylase activities, were found to be determined by adrenal mitochondrial cytochrome P-450 particles. Carbon monoxide inhibition of 18- and 11beta-hydroxylation of deoxycorticosterone in these strains showed that the CO/O2 ratio causing 50% inhibition (i.e., Warburg's partition constant, K) was identical for 18- and 11beta-hydroxylation within a strain, but different for both 18- and 11 beta hydroxylation between strains. (K values were: S rats, 18-hydroxylation = 11.4 +/- 1.4; S rats, 11beta-hydroxylation = 11.0 +/- 1.2; R rats, 18-hydroxylation = 56.4 +/- 13.7; R rats, 11beta-hydroxylation = 46.7 +/- 11.7). This between-strain difference was unique for 18- and 11beta-hydroxylation; i.e., it was not seen with cholesterol side-chain cleavage or 21-hydroxylation. Moreover, the strain-specific K values for 18- and 11beta-hydroxylase and the strain-specific steroidogenic patterns due to the relative magnitudes of 18- and 11beta-hydroxylase activities segregated together in an F2 population. These data strongly suggest the same cytochrome P-450 is involved in both 18- and 11beta-hydroxylation and that this cytochrome is mutated between S and R rats. K values for the reaction corticosterone leads to 18-hydroxycorticosterone were different between S and R strains, indicating that the mutant cytochrome was also involved in this hydroxylation, but K values for the conversion corticosterone leads to aldosterone were not different between strains. This was interpreted to mean that each step in the sequence corticosterone leads to 18-hydroxycorticosterone leads to aldosterone was mediated by a different cytochrome, the K value for the second step being the lower and dominating the overall reaction. It was speculated that the second step could be a second hydroxylation at position 18 to yield 18,18-dihydroxycorticosterone which could be unstable and decompose into aldosterone and water.