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首页> 外文期刊>Biochemistry >NADPH dehydrogenase activity of p67PHOX, a cytosolic subunit of the leukocyte NADPH oxidase.
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NADPH dehydrogenase activity of p67PHOX, a cytosolic subunit of the leukocyte NADPH oxidase.

机译：p67PHOX（白细胞NADPH氧化酶的胞浆亚基）的NADPH脱氢酶活性。

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摘要

The leukocyte NADPH oxidase catalyzes the one-electron reduction of oxygen to O2- at the expense of NADPH. It is a multicomponent enzyme comprising a membrane-bound flavocytochrome (cytochrome b558) and at least four cytosolic components: p47PHOX, p67PHOX, p40PHOX, and Rac, a small GTPase. All the oxidase components except p40PHOX are required for enzyme activity. Many aspects of their function, however, are unclear. Using the electron acceptor ferricyanide, we found that recombinant p67PHOX from baculovirus-infected Sf9 cells could mediate the dehydrogenation of NADPH. NADPH dehydrogenation was not dependent on FAD and was insensitive to superoxide dismutase. Several control experiments showed that NADPH dehydrogenation was accomplished by p67PHOX, not by a trace contaminant in the p67PHOX preparation. The NADPH dehydrogenase activity of p67PHOX was proportional to enzyme concentration, and showed saturation kinetics with NADPH (Km 92 +/- 5 microM), but was inhibited at high concentrations of ferricyanide. NADH was also used as a substrate by p67PHOX (Km 123 +/- 38 microM). Taken together, these results show that p67PHOX is able to mediate pyridine nucleotide dehydrogenation. These findings raise the possibility that p67PHOX might participate directly in electron transfer between NADPH and the oxidase flavin.
机译：白细胞NADPH氧化酶以NADPH为代价将氧单电子还原为O2-。它是一种多组分酶，包含与膜结合的黄素细胞色素（cytochrome b558）和至少四个胞质组分：p47PHOX，p67PHOX，p40PHOX和Rac（一种小GTP酶）。除p40PHOX以外的所有氧化酶成分都是酶活性所必需的。但是，其功能的许多方面尚不清楚。使用电子受体铁氰化物，我们发现杆状病毒感染的Sf9细胞的重组p67PHOX可以介导NADPH的脱氢。 NADPH脱氢不依赖于FAD，并且对超氧化物歧化酶不敏感。几个对照实验表明，NADPH脱氢是通过p67PHOX完成的，而不是通过p67PHOX制剂中的微量污染物完成的。 p67PHOX的NADPH脱氢酶活性与酶的浓度成正比，并显示出NADPH（Km 92 +/- 5 microM）的饱和动力学，但在高浓度的铁氰化物下却被抑制。 p67PHOX（Km 123 +/- 38 microM）也将NADH用作底物。总之，这些结果表明p67PHOX能够介导吡啶核苷酸脱氢。这些发现增加了p67PHOX可能直接参与NADPH和氧化酶黄素之间电子转移的可能性。

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