Droux M, Miginiac-Maslow M, Jacquot J P, Gadal P, Crawford N A, Kosower N S, Buchanan B B
Arch Biochem Biophys. 1987 Jul;256(1):372-80. doi: 10.1016/0003-9861(87)90458-9.
The mechanism by which the ferredoxin-thioredoxin system activates the target enzyme, NADP-malate dehydrogenase, was investigated by analyzing the sulfhydryl status of individual protein components with [14C]iodoacetate and monobromobimane. The data indicate that ferredoxin-thioredoxin reductase (FTR)--an iron-sulfur enzyme present in oxygenic photosynthetic organisms--is the first member of a thiol chain that links light to enzyme regulation. FTR possesses a catalytically active dithiol group localized on the 13 kDa (similar) subunit, that occurs in all species investigated and accepts reducing equivalents from photoreduced ferredoxin and transfers them stoichiometrically to the disulfide form of thioredoxin m. The reduced thioredoxin m, in turn, reduces NADP-malate dehydrogenase, thereby converting it from an inactive (S-S) to an active (SH) form. The means by which FTR is able to combine electrons (from photoreduced ferredoxin) with protons (from the medium) to reduce its active disulfide group remains to be determined.
通过用[14C]碘乙酸盐和单溴代马来酰亚胺分析单个蛋白质组分的巯基状态，研究了铁氧化还原蛋白-硫氧还蛋白系统激活目标酶NADP-苹果酸脱氢酶的机制。数据表明，铁氧化还原蛋白-硫氧还蛋白还原酶（FTR）——一种存在于产氧光合生物中的铁硫酶——是将光与酶调节联系起来的硫醇链的第一个成员。FTR在13 kDa（类似）亚基上具有一个催化活性二硫醇基团，该基团存在于所有研究的物种中，接受来自光还原铁氧化还原蛋白的还原当量，并将它们化学计量地转移到硫氧还蛋白m的二硫键形式上。还原型硫氧还蛋白m反过来还原NADP-苹果酸脱氢酶，从而将其从无活性的（S-S）形式转化为活性的（SH）形式。FTR能够将（来自光还原铁氧化还原蛋白的）电子与（来自介质的）质子结合以还原其活性二硫键基团的方式仍有待确定。
