Rochelle L G, Morana S J, Kruszyna H, Russell M A, Wilcox D E, Smith R P
Department of Pharmacology and Toxicology, Dartmouth Medical School, Hanover, New Hampshire, USA.
J Pharmacol Exp Ther. 1995 Oct;275(1):48-52.
Interactions of nitric oxide (NO) with various cobalamin species have been examined, apparently for the first time, with both absorption and electron paramagnetic resonance spectroscopy. Only slight shifts in the absorption spectrum of hydroxocobalamin, B12a [Cb(III)], were produced by NO, but dramatic changes in the spectrum of B12r [Cb(III)] were found on addition of NO. The addition of NO shifted the spectrum of Cb(II) to one very similar to that of Cb(III), indicating the oxidation of Cb(II). The addition of NO to Cb(III) resulted in a novel, weak and previously undescribed electron paramagnetic resonance signal. Although it has not been fully characterized, this appears to represent a reversible complex in which NO is liganded to the Cb(III). When NO was added to Cb(II), its strong electron paramagnetic resonance spectrum was replaced by that of this novel species, consistent with oxidation of Cb(II) by NO and then binding of additional NO by the resulting Cb(III). Porcine, aortic endothelial cells were able to partially reduce Cb(III), and release to the supernatant a previously characterized superoxide cobalt(III) complex, but some Cb(II) remained with the cell fraction. These reactions of Cb species could play a role in altering intracellular and intratissue levels of NO.
一氧化氮（NO）与各种钴胺素种类的相互作用已通过吸收光谱和电子顺磁共振光谱进行了研究，这显然是首次。NO仅使羟钴胺素B12a [Cb(III)]的吸收光谱发生轻微偏移，但在添加NO后发现B12r [Cb(III)]的光谱发生了显著变化。添加NO使Cb(II)的光谱向与Cb(III)非常相似的方向偏移，表明Cb(II)被氧化。向Cb(III)中添加NO产生了一种新的、微弱且以前未描述过的电子顺磁共振信号。尽管尚未对其进行充分表征，但这似乎代表了一种可逆复合物，其中NO与Cb(III)配位。当向Cb(II)中添加NO时，其强电子顺磁共振光谱被这种新物种的光谱所取代，这与NO氧化Cb(II)然后所得Cb(III)结合额外的NO一致。猪主动脉内皮细胞能够部分还原Cb(III)，并将先前表征的超氧钴(III)复合物释放到上清液中，但仍有一些Cb(II)留在细胞组分中。Cb物种的这些反应可能在改变细胞内和组织内NO水平方面发挥作用。
