Syrtsova L A, Uzenskaja A M, Likhtenstein G I
Institute of Chemical Physics, Russian Academy of Sciences, Moscow region.
Biochem J. 1993 Mar 1;290 ( Pt 2)(Pt 2):627-31. doi: 10.1042/bj2900627.
The photoreduction, without reductant dithionite, of N2 to NH3 or acetylene to ethylene catalysed by nitrogenase in the presence of Mg2+. ATP, eosin and NADH in the light has been established. There is an optimum NADH concentration for each particular eosin concentration. When the ratio of the iron protein component of nitrogenase from Azotobacter vinelandii (Av2)/the molybdenum-iron protein component of nitrogenase from A. vinelandii (Av1) is equal to 3 for 4 x 10(-5) M eosin the optimum NADH concentration is 5 x 10(-4) M. The rate of photoreduction (per one electron) of acetylene or N2 under identical conditions was shown to be similar. The photoreductant-dependent ATPase activity, in the presence of a given photochemical system in the light, was revealed. Eosin is shown to be the inhibitor of the coupling site. Concentrations of 8 x 10(-6) -1 x 10(-4) M eosin do not inhibit the ATPase activity. The inhibition of substrate-reduction activity depends on the ratio of the nitrogenase components. Under conditions where the Av2/Av1 ratio is equal to 1 the rate of photochemical reduction is higher than in the presence of dithionite: the total electron flux through nitrogenase being increased 2.2-fold. We suggest that in this case the nitrogenase complex (1:1) works without dissociation.
在Mg2+、ATP、曙红和NADH存在且光照条件下，固氮酶可催化N2光还原为NH3或乙炔光还原为乙烯，且无需连二亚硫酸盐作为还原剂。现已确定，对于每种特定的曙红浓度，都存在一个最佳NADH浓度。当用于4×10(-5) M曙红时，来自棕色固氮菌的固氮酶铁蛋白组分（Av2）/来自棕色固氮菌的固氮酶钼铁蛋白组分（Av1）的比例等于3时，最佳NADH浓度为5×10(-4) M。结果表明，在相同条件下，乙炔或N2的光还原速率（每一个电子）相似。在光照下给定光化学系统存在的情况下，揭示了光还原剂依赖性ATP酶活性。曙红被证明是偶联位点的抑制剂。8×10(-6) -1×10(-4) M浓度的曙红不抑制ATP酶活性。底物还原活性的抑制取决于固氮酶组分的比例。在Av2/Av1比例等于1的条件下，光化学还原速率高于连二亚硫酸盐存在时的速率：通过固氮酶的总电子通量增加了2.2倍。我们认为，在这种情况下，固氮酶复合物（1:1）在不解离的情况下起作用。
