Properties of Aldosterone Synthase and the Regulation Mechanism in Adrenocortex.

尽管目前大量研究表明，促肾上腺皮质激素（ACTH）、肾素-血管紧张素系统、Na^+和K^+等多种因素对醛固酮的分泌有调控作用，但这些因素之间的相互关系及其调控机制尚未完全阐明。这主要是因为催化ALD形成的最后一步的酶的不确定性。最近的工作表明，纯化的细胞色素P-45011具有由脱氧皮质酮（DOC）或皮质酮（COR）形成ALD的活性，尽管很弱，除了类固醇的11 -和18-羟化的固有活性。然而，这一观察结果并不符合迄今为止所获得的许多其他观察结果，如z-肾小球（z.G）中ALD分泌受限，以及存在ALD形成的遗传性缺陷而不缺乏11 -羟化酶活性的患者等。 ...更多信息 Z.G和Z.fasciculata（Z.FR）在正常或异常生理条件下的线粒体ALD合成酶，并从牛和大鼠肾上腺皮质线粒体中分离和鉴定ALD合成酶。结果表明：（1）z.G细胞线粒体合成ALD的能力强于z.FR细胞，表现出明显的区域特异性。当超声处理两个区域的线粒体时，活性变得彼此相似，表明区域特异性减弱，z.G线粒体的完整性对正常ALD产生至关重要。2）Na耗尽和K充满大鼠的z.G线粒体将DOC或COR转化为18-OH COR和ALD的速率比K耗尽和Na充满大鼠高几倍至十倍。3）新的P-450物种49 K蛋白仅出现在刺激ALD生物合成的大鼠z.G的线粒体中。4）我们使用HPLC羟基磷灰石柱从Na耗尽的大鼠z. G中纯化了具有有效ALD合成活性的49 K蛋白。这与51 K蛋白（真正的细胞色素p-45011）完全分离，并被命名为ALD合酶。本实验室正在进行各种ALD生物合成途径诱导49 K蛋白的研究。少

Although a number of studies to date indicate that secretion of albosterone (ALD) is controlled by verious factors,such as ACTH,renin-angiotensin system,Na^+ and K^+,the interrelationship among these factors and the regulatory mechanism remain unresolved. This is mostly because of ambiguity of the enzyme which catalyzed the final step of ALD formation. Recent works have shown that purified cytochrome P-45011 has the activity of ALD formation from deoxycorticosterone (DOC) or corticosterone (COR), although very weak, besides intrinsic activities of 11 - and 18-hybroxylation of steroids. Such an observation,however,does not satisfy with many other observations so far obtained like ALD secretion limited in z-glomerulosa (z.G) and the presence of patients with inherited defect in ALD formation without deficiency in 11 -hydroxylase activity so on. We therefore incestigated the activities of individual reactions during the conversion of DOC to ALD in mitochondrial fractions of adrenocortical … More z.G and z.fasciculata (z.FR) of cow or rat under normal or abnormal physiological conditions,and then intended to isolate and characterize ALD synthase from bovine and rat adrenocortical mitochondria. Results we obtained were as follows:1) The intact mitochondria from z.G could produce more ALD than those from z.FR, showing distinct zonal specificity of ALD biosynthesis. When the mitochondria from both zones were sonicated, the activity became similar with each other, indicating the zonal specificity diminished and the integrity of the z.G mitochondria was essential to normal ALD production.2) Mitochondria from z.G of Na-depleted and K-repleted rats converted DOC or COR to 18-OH COR and ALD at several-to ten-fold higher retes than those of K-depleted and Na-repleted rats. However,the same preparations exhibited almost no difference in the 11 -and 18-hydroxylation of DOC.3) New P-450 species,49K protein,appeared in mitochondria only from z.G of rats with stimulated ALD biosynthesis.4) We purified 49K protein with a potent ALD synthesis activity from z.G of Na-depleted rats using HPLC hydroxylapatite column. This was completely separated from 51K protein (genuine cytochrome p-45011 ) and was designated as ALD synthase. The induction of 49K protein by various ftimuli of ALD biosynthesisare now in progress in our labolatory. Less