OXIDATION OF NITRIC-OXIDE IN AQUEOUS-SOLUTION TO NITRITE BUT NOT NITRATE - COMPARISON WITH ENZYMATICALLY FORMED NITRIC-OXIDE FROM L-ARGININE
OXIDATION OF NITRIC-OXIDE IN AQUEOUS-SOLUTION TO NITRITE BUT NOT NITRATE - COMPARISON WITH ENZYMATICALLY FORMED NITRIC-OXIDE FROM L-ARGININE
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DOI：
10.1073/pnas.90.17.8103
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发表时间：
1993-09-01
影响因子：
11.1
通讯作者：
BYRNS, RE
中科院分区：
文献类型：
--
作者：
IGNARRO, LJ;FUKUTO, JM;BYRNS, RE
一氧化氮（NO）在含氧水溶液中具有较短的半衰期，这通常归因于快速氧化为NO2-和NO3-。通常认为NO在水溶液中的化学命运与空气中相同，其中NO被氧化为NO2，然后二聚为N2 O 4。 然后水与N2 O 4反应生成NO2-和NO3-。我们在这里报告，在含氧的水溶液中，NO主要被氧化为NO2-，很少或根本没有形成NO3-。在氧合血红蛋白或氧合肌红蛋白存在下，NO和NO2-被完全氧化为NO3-。高铁血红蛋白在这方面没有活性。来自大鼠小脑的未纯化的胞质级分，其中包含组成型NO合酶活性，催化L-精氨酸主要转化为NO3-（NO2-/NO3-比= 0.25）。经过DEAE-Sephacel层析或使用2 '，5'-ADP-Sepharose 4 B的亲和层析后，含有NO合酶活性的活性组分分别催化L-精氨酸主要转化为NO2-（NO2-/NO3-比= 5.6）或仅转化为NO2-。未纯化的大鼠肺泡巨噬细胞胞液催化L-精氨酸转化为NO2-，而不形成NO3-。向所有酶反应混合物中添加30 μ M氧合血红蛋白导致主要形成NO3-（NO2-/NO3-比率= 0.09至0.20）。氰化物离子从氧合血红蛋白上的结合位点取代NO2-，抑制NO3-的形成，从而使NO2-积累。这些观察结果清楚地表明，在有氧水溶液中的NO的主要分解产物是NO2-和进一步氧化为NO3-需要存在额外的氧化物种，如氧化血红素蛋白。
Nitric oxide (NO) in oxygen-containing aqueous solution has a short half-life that is often attributed to a rapid oxidation to both NO2- and NO3-. The chemical fate of NO in aqueous solution is often assumed to be the same as that in air, where NO is oxidized to NO2 followed by dimerization to N2O4. Water then reacts with N2O4 to form both NO2- and NO3-. We report here that NO in aqueous solution containing oxygen is oxidized primarily to NO2- with little or no formation of NO3-. In the presence of oxyhemoglobin or oxymyoglobin, however, NO and NO2- were oxidized completely to NO3-. Methemoglobin was inactive in this regard. The unpurified cytosolic fraction from rat cerebellum, which contains constitutive NO synthase activity, catalyzed the conversion of L-arginine primarily to NO3- (NO2-/NO3- ratio = 0.25). After chromatography on DEAE-Sephacel or affinity chromatography using 2',5'-ADP-Sepharose 4B, active fractions containing NO synthase activity catalyzed the conversion Of L-arginine primarily to NO2- (NO2-/NO3- ratio = 5.6) or only to NO2-, respectively. Unpurified cytosol from activated rat alveolar macrophages catalyzed the conversion of L-arginine to NO2- without formation of NO3-. Addition of 30 muM oxyhemoglobin to all enzyme reaction mixtures resulted in the formation primarily of NO3- (NO2-/NO3- ratio = 0.09 to 0.20). Cyanide ion, which displaces NO2- from its binding sites on oxyhemoglobin, inhibited the formation of NO3-, thereby allowing NO2-to accumulate. These observations indicate clearly that the primary decomposition product of NO in aerobic aqueous solution is NO2- and that further oxidation to NO3- requires the presence of additional oxidizing species such as oxyhemoproteins.