MICROSOMAL CYTOCHROME-P-450 FROM NEONATAL PIG TESTIS - 2 ENZYMATIC-ACTIVITIES (17-ALPHA-HYDROXYLASE AND C-17,C-20-LYASE) ASSOCIATED WITH ONE PROTEIN
MICROSOMAL CYTOCHROME-P-450 FROM NEONATAL PIG TESTIS - 2 ENZYMATIC-ACTIVITIES (17-ALPHA-HYDROXYLASE AND C-17,C-20-LYASE) ASSOCIATED WITH ONE PROTEIN
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DOI：
10.1021/bi00517a014
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发表时间：
1981-01-01
期刊：
影响因子：
2.9
通讯作者：
HALL, PF
中科院分区：
文献类型：
--
作者：
NAKAJIN, S;SHIVELY, JE;HALL, PF
进行研究以检验来自睾丸微粒体的细胞色素P-450由具有2种酶活性的单一蛋白质（17 α-β）组成的假设。羟化酶和C17，20-裂解酶）。获得了支持这一假设的三条证据。通过与抗P-450 IgG的免疫化学标准（免疫扩散上的同一性线和免疫电泳上的单一条带），通过证明单个NH 2末端氨基酸（甲硫氨酸）和在NH 2末端发现16个单个氨基酸，该酶似乎是同质的。pH和温度的最佳值对于两种酶活性是相同的（pH 7.25和37 ℃）。温度在30 - 44 ℃之间。C降低了这两种活性，以这样一种方式，羟化酶裂解酶的比例是相同的，在所有温度下测试。多种抑制剂以相同的程度影响两种活性：2种竞争性抑制剂（SU 8000，0.04 μ M; SU 10603，0.3 μ M）的Ki值对于羟化酶和裂解酶是相同的;一氧化碳抑制的分配系数对于羟化酶和裂解酶是相似的（20 ± 0.5 μ M）。2和27 .+-。3）;抗P-450（血清和IgG）对两种活性的抑制程度相同，各种特异性较低的抑制剂也是如此。显然，来自新生猪睾丸微粒体的单个血红素蛋白（细胞色素P-450）催化2个反应（羟化酶和裂解酶），这是睾丸合成雄激素的连续步骤，导致C21前体转化为C19类固醇激素。
Studies were performed to test the hypothesis that cytochrome P-450 from testicular microsomes consists of a single protein with 2 enzymatic activities (17.alpha.-hydroxylase and C17,20-lyase). Three lines of evidence to support the hypothesis were obtained. The enzyme appears to be homogeneous by immunochemical criteria with anti-P-450 IgG (line of identity on immunodiffusion and a single band on immunoelectrophoresis), by demonstration of a single NH2-terminal amino acid (methionine) and the finding of 16 single amino acids at the NH2 terminus. Optima for pH and temperature are the same for both enzymatic activities (pH 7.25 and 37.degree. C), and temperatures between 30 and 44.degree. C decreased both activities in such a way that the ratio of hydroxylase to lyase was the same at all temperatures tested. A variety of inhibitors affect both activities to the same extent: Ki values for 2 competitive inhibitors (SU 8000, 0.04 .mu.M; SU 10603, 0.3 .mu.M) are the same for hydroxylase and lyase; partition coefficients for inhibition by carbon monoxide are similar for hydroxylase and lyase (20 .+-. 2 and 27 .+-. 3); anti-P-450 (serum and IgG) causes inhibition of both activities to the same extent, and the same is true of a variety of less specific inhibitors. Apparently a single heme protein (cytochrome P-450) from microsomes of neonatal pig testis catalyzes 2 reactions (hydroxylase and lyase) which are sequential steps in the synthesis of androgens by the testis leading to conversion of C21 precursors to C19 steroid hormones.