Uppu R M, Squadrito G L, Pryor W A
The Biodynamics Institute, Louisiana State University, Baton Rouge, Louisiana 70803-1800. USA.
Arch Biochem Biophys. 1996 Mar 15;327(2):335-43. doi: 10.1006/abbi.1996.0131.
Stopped-flow kinetic studies of the isomerization of peroxynitrite to give nitrate have been performed in carbonate-enriched buffers using pH jump and carbonic anhydrase as probes. The data are consistent with the reaction of CO2 and the peroxynitrite anion rapidly forming an unstable nitrosoperoxy-carbonate anion adduct, O=N-OOCO2- (1). The CO2 catalysis of the isomerization of peroxynitrite is not accompanied by the formation of nitrite, hydrogen peroxide, or other hydroperoxidic material like peroxycarbonate. The reaction proceeds via the transient formation of an oxidant or oxidants that is (are) capable of promoting electrophilic nitration reactions. We propose that O=N-OOCO2- rearranges to give a nitrocarbonate anion, O2N-OCO2- (2) which in turn, may serve as the proximal oxidant in biological systems that produce peroxynitrite. At least four different mechanistic classes of reactions that have been ascribed to peroxynitrite can be envisioned to involve 2: (a) hydrolysis to nitrate, (b) one-electron or (c) two-electron oxidations, and (d) electrophilic nitration. Given the fast reaction of peroxynitrite with carbon dioxide and the ubiquitous presence of the latter, the role of CO2 cannot be neglected in complex peroxynitrite reactions in vitro and in vivo.
利用pH跃变和碳酸酐酶作为探针，在富含碳酸盐的缓冲液中对过氧亚硝酸盐异构化为硝酸盐进行了停流动力学研究。数据表明，二氧化碳与过氧亚硝酸根阴离子迅速反应，形成不稳定的亚硝基过氧碳酸根阴离子加合物O=N-OOCO2-（1）。二氧化碳对过氧亚硝酸盐异构化的催化作用并不伴随着亚硝酸盐、过氧化氢或其他过氧物质（如过氧碳酸盐）的形成。该反应通过一种或多种能够促进亲电硝化反应的氧化剂的瞬时形成来进行。我们认为，O=N-OOCO2-重排生成硝基碳酸根阴离子O2N-OCO2-（2），而后者反过来可能是产生过氧亚硝酸盐的生物系统中的近端氧化剂。可以设想，至少有四种不同的、归因于过氧亚硝酸盐的反应机制类别涉及到2：（a）水解为硝酸盐，（b）单电子或（c）双电子氧化，以及（d）亲电硝化。鉴于过氧亚硝酸盐与二氧化碳的快速反应以及后者的普遍存在，在体外和体内复杂的过氧亚硝酸盐反应中，二氧化碳的作用不容忽视。
