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固氮酶是怎样在常温常压下摄取空气中的氮,并把它转化为氨的?这是个重大的科学问题。 本文根据固氮酶已知的反应和络合催化原理,讨论了固氮酶的作用机理和活性中心结构。提出了由类立方烷结构的Fe_2S_2·Mo_2O_2八原子簇构成的一对偶联的两钼一铁(2Mo-1Fe)三核活性中心模型,并用以阐明固氮酶各种底物的酶促还原反应机理,包括放氢反应机理,以及CO不抑制放氢反应而对其他底物的酶促还原反应显出竞争性与非竞争性的混合型抑制特征的原因。 提出了二步ATP驱动的电子活化机理,并用以解释ATP/2e~-的比值和不需还原剂的ATP酶促水解。指出了这二步ATP驱动的“电子活化”与绿色植物光合作用中的二步光驱动电子传递的紧密对应关系。
Nitrogenase is how to ingest nitrogen in the air at normal temperature and pressure and turn it into ammonia? This is a major scientific problem. According to the known reaction and complexation catalytic principle of nitrogenase, the mechanism and active center structure of nitrogenase were discussed. A pair of coupled two molybdenum-iron (2Mo-1Fe) trinuclear active center model consisting of Fe_2S_2 · Mo_2O_2 octahedral clusters with quaternary alkane structure was proposed and used to elucidate the enzymatic reduction mechanism of various substrates of nitrogenase , Including the mechanism of de-hydrogenation reaction, and the reason why CO does not inhibit the hydrogen-releasing reaction and shows competitive and non-competitive mixed-type inhibition characteristics for the enzymatic reduction of other substrates. A two-step ATP-driven electron activation mechanism was proposed and was used to explain the ATP / 2e ~ - ratio and ATP enzymatic hydrolysis without reductant. The close correspondence between the two-step ATP driven “electron activation” and the two-step photo-driven electron transfer in photosynthesis of green plants is pointed out.