支链2-氧代酸与牛血清白蛋白的结合。

Binding of branched-chain 2-oxo acids to bovine serum albumin.

作者信息

Livesey G, Lund P

出版信息

Biochem J. 1982 Apr 15;204(1):265-72. doi: 10.1042/bj2040265.

DOI:10.1042/bj2040265

PMID:7115325

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1158341/

Abstract

Binding of branched-chain 2-oxo acids to defatted bovine serum albumin was shown by gel chromatography and equilibrium dialysis. 2. Equilibrium-dialysis data suggest a two-side model for binding in Krebs-Henseleit saline at 37 degrees C with n1 = 1 and n2 = 5. Site association constants were: 4-methyl-2-oxovalerate, k1 = 8.7 x 10(3) M-1, k2 = 0.09 x 10(3) M-1; 3-methyl-2-oxovalerate, k1 = 9.8 x 10(3) M-1, k2 = 0.08 x 10(3) M-1; 3-methyl-2-oxobutyrate, k1 = 1.27 x 10(3) M-1, k2 = less than 0.05 x 10(3) M-1. 3. Binding of 4-methyl-2-oxovalerate to defatted albumin in a phosphate-buffered saline, pH 7.4, gave the following thermodynamic parameters: primary site delta H0(1) = -28.6kJ . mol-1 and delta S0(1) = -15.2J . mol-1 . K-1 (delta G0(1) = -24.0kJ . mol-1 at 37 degrees C) and secondary sites delta H0(2) = -25.4kJ . mol-1 and delta S0(2) = -46.1J . mol-1 . K-1 (delta G0(1) = -11.2kJ . mol-1 at 37 degrees C). Thus binding at both sites is temperature-dependent and increases with decreasing temperature. 4. Inhibition studies suggest that 4-methyl-2-oxovalerate may associate with defatted albumin at a binding site for medium-chain fatty acids. 5. Binding of the 2-oxo acids in bovine, rat and human plasma follows a similar pattern to binding to defatted albumin. The proportion bound in bovine and human plasma is much higher than in rat plasma. 6. Binding to plasma protein, and not active transport, explains the high concentration of branched-chain 2-oxo acids leaving rat skeletal muscle relative to the concentration within the tissue, but does not explain the 2-oxo acid concentration gradient between plasma and liver.

摘要

通过凝胶色谱法和平衡透析法表明，支链2-氧代酸与脱脂牛血清白蛋白发生了结合。2. 平衡透析数据表明，在37℃的克雷布斯-亨泽莱特盐溶液中，结合存在双侧模型，n1 = 1，n2 = 5。位点缔合常数为：4-甲基-2-氧代戊酸，k1 = 8.7×10³ M⁻¹，k2 = 0.09×10³ M⁻¹；3-甲基-2-氧代戊酸，k1 = 9.8×10³ M⁻¹，k2 = 0.08×10³ M⁻¹；3-甲基-2-氧代丁酸，k1 = 1.27×10³ M⁻¹，k2＜0.05×10³ M⁻¹。3. 在pH 7.4的磷酸盐缓冲盐溶液中，4-甲基-2-氧代戊酸与脱脂白蛋白的结合给出了以下热力学参数：主要位点ΔH⁰(1) = -28.⁶kJ·mol⁻¹，ΔS⁰(1) = -15.²J·mol⁻¹·K⁻¹（37℃时ΔG⁰(1) = -24.⁰kJ·mol⁻¹），次要位点ΔH⁰(2) = -25.⁴kJ·mol⁻¹，ΔS⁰(2) = -46.¹J·mol⁻¹·K⁻¹（37℃时ΔG⁰(1) = -11.²kJ·mol⁻¹）。因此，两个位点的结合都与温度有关，且随温度降低而增加。4. 抑制研究表明，4-甲基-2-氧代戊酸可能在中链脂肪酸的结合位点与脱脂白蛋白缔合。5. 2-氧代酸在牛、大鼠和人血浆中的结合模式与与脱脂白蛋白的结合相似。在牛和人血浆中结合的比例远高于大鼠血浆。6. 与血浆蛋白的结合而非主动转运，解释了相对于组织内浓度而言，离开大鼠骨骼肌的支链2-氧代酸浓度较高的原因，但无法解释血浆与肝脏之间的2-氧代酸浓度梯度。