Xue H, Wu X F, Wong J T
Department of Biochemistry, University of Toronto, Canada.
Artif Organs. 1992 Aug;16(4):427-31. doi: 10.1111/j.1525-1594.1992.tb00545.x.
Phytate was digested by wheat bran phytase to yield inositol tetrakisphosphate. Periodate-oxidized inositol tetrakisphosphate (oxyIP4) was coupled by means of reductive alkylation to hemoglobin and the covalent dextran-hemoglobin conjugate to yield the rightshifted (rs) compounds rsHb and rsDxHb, respectively. The variations of the oxygen dissociation curves of these molecules with pH and temperature were compared to those of hemoglobin. The variations with pH were found to be less pronounced for these rightshifted forms. An extensive decrease in the half-saturation oxygen tension was observed, however, with both rsHb and rsDxHb, as in the case of unmodified Hb. Modification of hemoglobin by oxyIP4 at the polyphosphate site was suggested by the lack of a further rightshifting effect of phytate on rsHb, and by the similarity between the difference spectrum of rs-methemoglobin and the difference spectrum induced by the addition of phytate.
植酸盐被麦麸植酸酶消化产生肌醇四磷酸。高碘酸盐氧化的肌醇四磷酸（oxyIP4）通过还原烷基化与血红蛋白偶联，共价葡聚糖 - 血红蛋白共轭物分别产生右移（rs）化合物rsHb和rsDxHb。将这些分子的氧解离曲线随pH和温度的变化与血红蛋白的变化进行比较。发现这些右移形式随pH的变化不太明显。然而，与未修饰的Hb一样，rsHb和rsDxHb的半饱和氧张力均出现大幅下降。植酸盐对rsHb没有进一步的右移作用，以及rs - 高铁血红蛋白的差光谱与添加植酸盐诱导的差光谱之间的相似性，表明oxyIP4在多磷酸盐位点对血红蛋白进行了修饰。
