Kawamura A, Guo J, Itagaki Y, Bell C, Wang Y, Haupert G T, Magil S, Gallagher R T, Berova N, Nakanishi K
Department of Chemistry, Columbia University, New York, NY 10027, USA.
Proc Natl Acad Sci U S A. 1999 Jun 8;96(12):6654-9. doi: 10.1073/pnas.96.12.6654.
The ouabain-like sodium pump inhibitor in mammals (so-called "endogenous ouabain") has been considered a subtle structural isomer of ouabain. Its structural investigation, however, has long been hindered by the paucity of sample material. Our recent purification of endogenous ouabain (3 micrograms) from bovine hypothalamus allowed the measurement of its 1H-NMR. The obtained spectrum as well as reexamination of past microscale structural studies on endogenous ouabain led us to identify the purified material as ouabain in an unusual manner. It turned out that the structural analysis had been complicated by a facile ouabain-borate complexation in borosilicate glassware. In retrospect, it is not surprising that the polyhydroxylated ouabain molecule serves as a polydentate ligand to inorganic species. In its physiological environment, ouabain may exist as some unknown complex. The chemical species giving rise to the reported biological activities of hypothalamic inhibitory factor preparations remain to be clarified.
哺乳动物体内类似哇巴因的钠泵抑制剂（即所谓的“内源性哇巴因”）一直被认为是哇巴因的一种细微结构异构体。然而，由于样品材料匮乏，其结构研究长期受到阻碍。我们最近从牛下丘脑纯化出内源性哇巴因（3微克），从而得以测量其1H-NMR。所获得的光谱以及对过去关于内源性哇巴因的微量结构研究的重新审视，使我们以一种不同寻常的方式鉴定出纯化后的物质为哇巴因。结果表明，硼硅酸盐玻璃器皿中哇巴因与硼的轻易络合使结构分析变得复杂。回想起来，多羟基化的哇巴因分子作为无机物种的多齿配体并不奇怪。在其生理环境中，哇巴因可能以某种未知络合物的形式存在。导致下丘脑抑制因子制剂所报道的生物活性的化学物质仍有待阐明。
