Faculty of Chemistry, Jagiellonian University, Gronostajowa 2, 30-387, Kraków, Poland.
Department of Chemistry and Pharmacy, University of Erlangen-Nuremberg, Egerlandstrasse 1, 91058, Erlangen, Germany.
J Biol Inorg Chem. 2018 May;23(3):377-383. doi: 10.1007/s00775-018-1540-1. Epub 2018 Feb 12.
Despite detailed studies on nitroxylcobalamin (CblNO) formation, the possible intracellular generation of CblNO via reduction of nitrocobalamin (CblNO) remains questionable. To study this further, spectroscopic studies on the reaction of CblNO with the intracellular antioxidant ascorbic acid (HAsc) were performed in aqueous solution at pH < 5.0. It was found that nitroxylcobalamin is the final product of this interaction, which is not just a simple reaction but a rather complex chemical process. We clearly show that an excess of nitrite suppresses the formation of CblNO, from which it follows that ascorbic acid cannot reduce coordinated nitrite. We propose that under the influence of ascorbic acid, nitrocobalamin is reduced to Cbl(II) and nitric oxide (NO), which can subsequently react rapidly to form CblNO. It was further shown that this system requires anaerobic conditions as a result of the rapid oxidation of both Cbl(II) and CblNO.
尽管对硝钴胺素（CblNO）的形成进行了详细的研究，但通过还原亚硝钴胺素（CblNO）在细胞内产生 CblNO 的可能性仍存在疑问。为了进一步研究这一点，在 pH < 5.0 的水溶液中对 CblNO 与细胞内抗氧化剂抗坏血酸（HAsc）的反应进行了光谱研究。结果发现，氮氧钴胺素是这种相互作用的最终产物，这不仅仅是一个简单的反应，而是一个相当复杂的化学过程。我们清楚地表明，过量的亚硝酸盐会抑制 CblNO 的形成，由此可以推断出抗坏血酸不能还原配位的亚硝酸盐。我们提出，在抗坏血酸的影响下，亚硝钴胺素被还原为 Cbl(II)和一氧化氮（NO），随后它们可以迅速反应形成 CblNO。进一步表明，由于 Cbl(II)和 CblNO 的快速氧化，该系统需要无氧条件。
