Rembold H, Buff K, Hennings G
Clin Chim Acta. 1977 May 2;76(3):329-38. doi: 10.1016/0009-8981(77)90159-0.
Binding behaviour of labelled biopterin, 6,7-dimethylpterin, 2,4-diamino-6,7-dimethylpteridin, and of their 5,6,7,8-tetrahydro derivatives was studied with human serum proteins. Binding capacity of serum proteins is in the range of 5 x 10-10--10-3 M without saturation for all these pteridines. Preincubation or competition with tetrahydrobiopterin does not influence binding of tetrahydro-6,7-dimethylpterin in these concentrations. The bulk of pteridines is bound through unspecific adsorption. Only at concentrations of less than 0.8 x 10-8 M does high affinity binding seem to be possible, corresponding to about 300 pmol/g protein, whereas physiological biopterin concentration is near 2 x 10-8 M. The binding proteins are very sensitive to ageing and lose their capacity during purification, whereas unspecific binding to serum proteins is only weakly influenced by alteration of salt concentration, pH, or temperature. Attempts to partially purify the binding proteins by ion exchange, dextran gel (Sephadex G-200), or affinity chromatography, demonstrate a specificity of tetrahydropterins for the alpha2-macroglobulin fraction. Due to the high lability of this protein fraction and of pteridine binding, purification of a protein which specifically binds tetrahydrobiopterin was not achieved.
研究了标记的生物蝶呤、6,7 - 二甲基蝶呤、2,4 - 二氨基 - 6,7 - 二甲基蝶啶及其5,6,7,8 - 四氢衍生物与人血清蛋白的结合行为。对于所有这些蝶啶，血清蛋白的结合能力在5×10⁻¹⁰ - 10⁻³ M范围内，且无饱和现象。在这些浓度下，预先孵育或与四氢生物蝶呤竞争并不影响四氢 - 6,7 - 二甲基蝶呤的结合。大部分蝶啶是通过非特异性吸附结合的。仅在浓度低于0.8×10⁻⁸ M时，才可能存在高亲和力结合，约为300 pmol/g蛋白质，而生理状态下生物蝶呤浓度接近2×10⁻⁸ M。结合蛋白对老化非常敏感，在纯化过程中会丧失其结合能力，而非特异性结合血清蛋白仅受盐浓度、pH值或温度变化的微弱影响。尝试通过离子交换、葡聚糖凝胶（Sephadex G - 200）或亲和层析对结合蛋白进行部分纯化，结果表明四氢蝶呤对α2 - 巨球蛋白组分具有特异性。由于该蛋白组分以及蝶呤结合的高度不稳定性，未能成功纯化出特异性结合四氢生物蝶呤的蛋白质。
