Wu X B, Brüne B, von Appen F, Ullrich V
University of Konstanz, Faculty of Biology, Federal Republic of Germany.
Arch Biochem Biophys. 1992 Apr;294(1):75-82. doi: 10.1016/0003-9861(92)90139-n.
Soluble guanylate cyclase of human platelets was stimulated by thiol oxidizing compounds like diamide and the reactive disulfide 4, 4'-dithiodipyridine. Activation followed a bell-shaped curve, revealing somewhat different optimum concentrations for each compound, although in both cases, higher concentrations were inhibitory. Diamide at a concentration of 100 microM transiently activated the enzyme. In the presence of moderate concentrations of diamide and 4,4'-dithiodipyridine, causing a two- to fourfold activation by themselves, the stimulatory activity of NO-releasing compounds like sodium nitroprusside was potentiated. In contrast, higher concentrations of thiol oxidizing compounds inhibited the NO-stimulated activation of soluble guanylate cyclase. Activation of guanylate cyclase was accompanied by a reduction in reduced glutathione and a concomitant formation of protein-bound glutathione (protein-SSG). Both compounds showed an activating potency as long as reduced glutathione remained, leading to inhibition of the enzyme just when all reduced glutathione was oxidized. Activation was reversible while reduced glutathione recovered and protein-SSG disappeared. We propose that diamide or reactive disulfides and other thiol oxidizing compounds inducing thiol-disulfide exchange activate soluble guanylate cyclase. In this respect partial oxidation is associated with enzyme activation, whereas massive oxidation results in loss of enzymatic activity. Physiologically, partial disulfide formation may amplify the signal toward NO as the endogenous activator of soluble guanylate cyclase.
二硫代氨基甲酸盐和反应性二硫化物4,4'-二硫代二吡啶等硫醇氧化化合物可刺激人血小板中的可溶性鸟苷酸环化酶。激活呈现钟形曲线，每种化合物的最佳浓度略有不同，不过在两种情况下，较高浓度均具有抑制作用。浓度为100微摩尔的二硫代氨基甲酸盐可短暂激活该酶。在中等浓度的二硫代氨基甲酸盐和4,4'-二硫代二吡啶存在下，它们自身可引起两到四倍的激活，像硝普钠这样的释放一氧化氮的化合物的刺激活性会增强。相比之下，较高浓度的硫醇氧化化合物会抑制一氧化氮刺激的可溶性鸟苷酸环化酶的激活。鸟苷酸环化酶的激活伴随着还原型谷胱甘肽的减少以及蛋白质结合型谷胱甘肽（蛋白质-SSG）的同时形成。只要还原型谷胱甘肽存在，这两种化合物都表现出激活能力，而当所有还原型谷胱甘肽被氧化时，就会导致酶的抑制。随着还原型谷胱甘肽的恢复和蛋白质-SSG的消失，激活是可逆的。我们提出，二硫代氨基甲酸盐或反应性二硫化物以及其他诱导硫醇-二硫键交换的硫醇氧化化合物可激活可溶性鸟苷酸环化酶。在这方面，部分氧化与酶的激活相关，而大量氧化则导致酶活性丧失。从生理角度来看，部分二硫键的形成可能会放大朝向一氧化氮的信号，一氧化氮是可溶性鸟苷酸环化酶的内源性激活剂。
