Jackson M A, Tiedje J M, Averill B A
Department of Chemistry, University of Virginia, Charlottesville 22901.
FEBS Lett. 1991 Oct 7;291(1):41-4. doi: 10.1016/0014-5793(91)81099-t.
Reduction of NO2- by the Cu-containing nitrite reductase from Achromobacter cycloclastes produces NO as the primary product initially, but as NO accumulates, NO production levels-off and N2O production becomes significant. Reaction of the enzyme with NO2- in the presence of NO increases the amount of N2O product significantly, while trapping the NO product as nitrosylhemoglobin or rapid removal of NO by sparging results in no detectable N2O production. Reaction of the enzyme with 15NO2- in the presence of 14NO results in rapid formation of the mixed isotope product (14N, 15N)O in ca. 45% yield. In contrast, the presence or absence of NO has no effect on N2O production by a prototypical heme cd1-containing nitrite reductase. These results are consistent with formation of a labile Cu(+)-NO+ species in the copper enzyme, which normally decomposes to NO. Production of N2O requires that the released NO must rebind to the enzyme to combine with a second NO2- or a species derived therefrom.
来自解环无色杆菌的含铜亚硝酸还原酶还原NO₂⁻时，最初产生的主要产物是NO，但随着NO的积累，NO的产生趋于平稳，N₂O的产生变得显著。在NO存在的情况下，该酶与NO₂⁻反应会显著增加N₂O产物的量，而将NO产物捕获为亚硝酰血红蛋白或通过鼓泡快速去除NO则不会产生可检测到的N₂O。在¹⁴NO存在的情况下，该酶与¹⁵NO₂⁻反应会快速形成混合同位素产物(¹⁴N,¹⁵N)O，产率约为45%。相比之下，NO的存在与否对典型的含血红素cd₁亚硝酸还原酶产生N₂O没有影响。这些结果与铜酶中形成不稳定的Cu(⁺)-NO⁺物种一致，该物种通常分解为NO。N₂O的产生要求释放的NO必须重新结合到酶上，以便与第二个NO₂⁻或由此衍生的物种结合。
