Department of Biochemistry and Biophysics, Stockholm University, Sweden.
Department of Organic Chemistry, Stockholm University, Sweden.
FEBS Lett. 2019 Jun;593(12):1351-1359. doi: 10.1002/1873-3468.13436. Epub 2019 May 29.
A key step of denitrification, the reduction of toxic nitric oxide to nitrous oxide, is catalysed by cytochrome c-dependent NO reductase (cNOR). cNOR contains four redox-active cofactors: three hemes and a nonheme iron (Fe ). Heme b and Fe constitute the active site, but the specific mechanism of NO-binding events and reduction is under debate. Here, we used a recently constructed, fully folded and hemylated cNOR variant that lacks Fe to investigate the role of Fe during catalysis. We show that in the Fe -less cNOR, binding of both NO and O to heme b still occurs but further reduction is impaired, although to a lesser degree for O than for NO. Implications for the catalytic mechanisms of cNOR are discussed.
反硝化作用的一个关键步骤是将有毒的一氧化氮还原为一氧化二氮，该过程由细胞色素 c 依赖型一氧化氮还原酶（cNOR）催化。cNOR 包含四个氧化还原活性辅因子：三个血红素和一个非血红素铁（Fe ）。血红素 b 和 Fe 构成活性位点，但 NO 结合事件和还原的具体机制仍存在争议。在这里，我们使用最近构建的、完全折叠和血红素化的 cNOR 变体，该变体缺乏 Fe ，来研究 Fe 在催化过程中的作用。我们表明，在无 Fe 的 cNOR 中，血红素 b 仍然能够结合 NO 和 O，但进一步的还原受到了阻碍，尽管 O 的阻碍程度比 NO 小。这对 cNOR 的催化机制具有启示意义。
