Jurtshuk P, Old L
J Bacteriol. 1968 May;95(5):1790-7. doi: 10.1128/jb.95.5.1790-1797.1968.
The spectrophotometric oxidation of horse heart ferrocytochrome c was examined by use of the particulate electron transport fraction (R(3)) of Azotobacter vinelandii strain O. Unlike cytochrome c, purified preparations of native Azotobacter cytochromes c(4) + c(5) were oxidized only slowly by the electron transport fraction. The oxidation of mammalian cytochrome c proceeded at an appreciable rate and displayed "apparent" first-order kinetics at a pH optimum of 9.0 with tris(hydroxymethyl)aminomethane-chloride buffer. The calculated V(max) value was 0.22 mumole of cytochrome c oxidized per min per mg of protein (25 C) and a K(m) value for cytochrome c of 2.3 x 10(-5)m was obtained. Ferricytochrome c was a "strict" competitive inhibitor for this oxidation. Cytochrome c oxidation by the Azotobacter electron transport system was markedly sensitive to cyanide, azide, and hydroxylamine, although carbon monoxide inhibition could not be demonstrated. It was sensitive also to high concentrations of phosphate, ethylenediaminetetraacetate, and some metal cations. "Aging" or prolonged storage of the Azotobacter R(3) fraction, at 4 C for 10 days, resulted in a threefold increase in specific activity. The cytochrome c peroxidase type of reaction did not occur with the R(3) electron transport fraction.
利用棕色固氮菌O菌株的颗粒状电子传递组分（R(3)）研究了马心亚铁细胞色素c的分光光度氧化。与细胞色素c不同，天然棕色固氮菌细胞色素c(4)+c(5)的纯化制剂仅被电子传递组分缓慢氧化。哺乳动物细胞色素c的氧化以可观的速率进行，在以三（羟甲基）氨基甲烷 - 氯化物缓冲液为最佳pH值9.0时表现出“表观”一级动力学。计算得出的V(max)值为每分钟每毫克蛋白质氧化0.22微摩尔细胞色素c（25℃），细胞色素c的K(m)值为2.3×10(-5)m。高铁细胞色素c是这种氧化的“严格”竞争性抑制剂。棕色固氮菌电子传递系统对细胞色素c的氧化对氰化物、叠氮化物和羟胺明显敏感，尽管无法证明一氧化碳抑制作用。它对高浓度的磷酸盐、乙二胺四乙酸和一些金属阳离子也敏感。棕色固氮菌R(3)组分在4℃下“老化”或长时间储存10天会导致比活性增加三倍。R(3)电子传递组分未发生细胞色素c过氧化物酶类型的反应。
