Departamento de Química Biológica, Facultad de Farmacia y Bioquímica, Universidad de Buenos Aires, Junín 956, 1113 Buenos Aires, Argentina.
Plant Physiol Biochem. 2011 Feb;49(2):124-30. doi: 10.1016/j.plaphy.2010.10.009. Epub 2010 Oct 31.
Nitrate reductase (NR), a committed enzyme in nitrate assimilation, is involved in the generation of nitric oxide (NO) in plants. In wheat leaf segments exposed to sodium nitroprusside (SNP) or S-nitrosoglutathione (GSNO), NR activity was significantly reduced to different degrees between 3 and 21 h, whereas its activity was partially recovered when the NO scavenger cPTIO was used. At 21 h, NR activity decreased from 38% with 10 μM SNP to 91% with 500 μM SNP, respect to the C values. S-nitrosoglutathione reduced NR activity between 18% and 26% only at 3 h. When added directly to the incubation solution, NR activity was quickly and strongly inhibited more than 90% by 10 or 50 μM SNP, whereas 10 μM GSNO reduced the enzyme activity an average of 50%, at 30 min of incubation. l-NAME and d-arginine (nitric oxide synthase (NOS) inhibitors) increased NR activity by 14% and 52% respectively, at 21 h of exposure, leading us to suppose that endogenous NOS-dependent NO formation could also be modulating NR activity. NR protein expression was not affected by 10 or 100 μM SNP at 3 or 21 h of incubation, whereas nitration of tyrosines was not detected in the NR protein. Nitrates, which content increased along the time in the tissues, could be exerting a role in this regulation.
硝酸还原酶（NR）是硝酸盐同化过程中的一种关键酶，参与植物中一氧化氮（NO）的生成。在暴露于硝普钠（SNP）或 S-亚硝基谷胱甘肽（GSNO）的小麦叶片中，NR 活性在 3 至 21 小时之间被不同程度地显著降低，而当使用 NO 清除剂 cPTIO 时，其活性部分恢复。在 21 小时时，NR 活性从 10 μM SNP 时的 38%降低到 500 μM SNP 时的 91%，相对于 C 值。S-亚硝基谷胱甘肽仅在 3 小时时将 NR 活性降低了 18%至 26%。当直接添加到孵育溶液中时，NR 活性被 10 或 50 μM SNP 迅速且强烈地抑制超过 90%，而 10 μM GSNO 在 30 分钟孵育时平均降低酶活性 50%。l-NAME 和 d-精氨酸（一氧化氮合酶（NOS）抑制剂）分别使 NR 活性增加 14%和 52%，在暴露 21 小时时，这表明内源性 NOS 依赖性 NO 形成也可能调节 NR 活性。NR 蛋白表达在 3 或 21 小时孵育时不受 10 或 100 μM SNP 的影响，而 NR 蛋白中的酪氨酸硝化未被检测到。硝酸盐的含量随着时间的推移在组织中增加，可能在这种调节中发挥作用。
