Abstract

Mutant strains of the filamentous cyanobacterium Anabaena strain PCC 7120 ΔHup (dc-Q193S and dc-R284H) with amino acid substitutions located in the vicinity of the FeMo cofactor of nitrogenase possess nitrogenase activity with a hydrogen production rate of approximately 18 μmol Н₂/(mg h), which is ~30% lower than that of the parental strain ΔHup. The photosynthetic activity of mutants is also reduced. Unlike the parental strain ΔHup, the dc-Q193S mutant shows a lower temperature optimum for hydrogen photoproduction. This difference is probably due to the lowered filament strength (fragmentation). Hydrogen photoproduction in mutants does not significantly differ from that of the parental strain in relation to the activation energy, light saturation constants (41–62 μmol quanta /(m² s)), and acetylene-induced inhibition. However, in contrast to the parental strain, hydrogen photoproduction in the mutant strains is not inhibited by molecular nitrogen, i.e., amino acid substitutions cause significant changes in the reaction requiring eight electrons (N₂ fixation). The possibility to use nitrogen or atmospheric air instead of argon in the hydrogen production is promising from the practical point of view, though reduced activity and increased fragility of filaments in the studied mutants limit the possibility of their practical use.

中文翻译：

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固氮酶中氨基酸取代的鱼腥藻PCC7120ΔHUP突变体的特征

摘要

丝状蓝藻的突变菌株鱼腥应变7120ΔHup（DC-Q193S和DC-R284H）与位于固氮的铁钼辅因子附近的氨基酸取代具有固氮酶活性约为18氢生产速率微摩尔Н ₂ /（ mg h），比亲本菌株ΔHup低约30％。突变体的光合作用活性也降低了。与亲本菌株ΔHup不同，dc-Q193S突变体显示出较低的温度，该温度最适合用于氢气的光生产。这种差异可能是由于降低的长丝强度（碎片）。突变体中的氢光生产与亲本菌株的光生产在活化能，光饱和常数（41–62μmol量子/（m²  s）），和乙炔诱导的抑制作用。但是，与亲本菌株相反，突变菌株中的氢光生产不受分子氮的抑制，即氨基酸取代引起需要八个电子的反应（N ₂固定）的显着变化。从实际的角度来看，在生产氢气的过程中使用氮气或大气代替氩气的可能性是有希望的，尽管所研究的突变体中丝的活性降低和脆性增加限制了其实际使用的可能性。