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首页> 外文期刊>Biochimica et Biophysica Acta. Protein Structure and Molecular Enzymology >Iron removal from monoferric human serum transferrins by 1, 2-dimethyl-3-hydroxypyridin-4-one, 1-hydroxypyridin-2-one and acetohydroxamic acid
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Iron removal from monoferric human serum transferrins by 1, 2-dimethyl-3-hydroxypyridin-4-one, 1-hydroxypyridin-2-one and acetohydroxamic acid

机译：1，2-二甲基-3-羟基吡啶-4-酮，1-羟基吡啶-2-酮和乙酰氧肟酸从单铁人血清转铁蛋白中除铁

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摘要

The kinetics of iron removal from both forms of human serum monoferric transferrin by three ligands, 1, 2-dimethyl-3-hydroxypyridin-4-one (L1), 1-hydroxypyridin-2-one and acetohydroxamic acid, have been evaluated at pH 7.4 and 25.0 ℃. In almost all cases the rate of iron removal follows simple saturation kinetics with respect to the ligand concentration. No spectroscopically distinct intermediates are observed during the iron removal reaction, which is consistent with a mechanism in which the rate-limiting step in iron removal is a protein conformational change. In the presence of chloride or perchlorate, most systems continue to follow simple saturation kinetics, but with significantly different k_(max) values. Chloride accelerates iron release from both transferrin binding sites, while perchlorate accelerates iron release from the C-terminal site but retards iron release from the N-terminal site. When the hydrochloride salt of L1 is used to prepare the L1 stock solution, the allosteric effect of the chloride produces a continuing increase in the rate of iron removal with increasing ligand concentration, so that one no longer observes simple saturation kinetics. A least squares fit of k_(obs) vs. the ligand concentration for L1250LCl shows that the allosteric effect of the chloride not only enhances the first-order term for iron removal but also doubles the apparent k_(max) for the saturation term. This supports the view that allosteric binding of anionic ligands contributes to the observed variation in k_(max) among different ligands. A detailed description of this allosteric effect is not yet possible because the effect varies significantly from system to system, depending upon the specific anion that is binding at the allosteric site, the ligand that is used to remove the iron, and the transferrin lobe from which iron is removed.
机译：已在pH值下评估了通过三种配体1,2-二甲基-3-羟基吡啶-4-酮（L1），1-羟基吡啶-2-酮和乙酰氧肟酸从两种形式的人血清单铁转铁蛋白中去除铁的动力学。 7.4和25.0℃。在几乎所有情况下，除铁速率均遵循相对于配体浓度的简单饱和动力学。除铁反应过程中未观察到光谱学上不同的中间体，这与除铁中的限速步骤是蛋白质构象变化的机理一致。在存在氯化物或高氯酸盐的情况下，大多数系统继续遵循简单的饱和动力学，但是k_（max）值却大不相同。氯化物会加速铁从两个转铁蛋白结合位点的释放，而高氯酸盐会加速铁从C端的释放，但会阻止铁从N端的释放。当使用L1的盐酸盐制备L1储备溶液时，氯化物的变构作用会随着配体浓度的增加而使铁的去除速率持续增加，因此不再能观察到简单的饱和动力学。 k_（obs）与L1250LCl的配体浓度的最小二乘拟合表明，氯化物的变构作用不仅增强了铁去除的一级项，而且使铁的表观k_（max）加倍。饱和度项。这支持以下观点：阴离子配体的变构结合有助于观察到不同配体之间k_（max）的变化。尚无法对此变构作用进行详细描述，因为该作用因系统而异，具体取决于在变构位点结合的特定阴离子，用于去除铁的配体以及从中去除铁的转铁蛋白叶铁被移除。

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