Neurohr K J, Young N M, Smith I C, Mantsch H H
Biochemistry. 1981 Jun 9;20(12):3499-504. doi: 10.1021/bi00515a030.
The binding kinetics of methyl alpha- and methyl beta-D-galactopyranoside to the anti-T lectin from peanuts were studied by 13C NMR, employing methyl galactopyranosides specifically enriched in 13C at C-1. Association and dissociation rate constants, as well as their activation parameters, are reported. The association rate constants, 4.6 X 10(4) M-1 s-1 for the alpha-galactopyranoside and 3.6 X 10(4) M-1 s-1 for the beta-galactopyranoside, are several orders of magnitude below those expected for a diffusion-controlled process. For both anomers, the association rate constant was temperature independent, implying that the association process occurs without a significant activation enthalpy. However, a considerable association activation entropy was found for both ligands. The dissociation rate constants were in the range of 9-46 s-1 within a temperature range of 5-35 degrees C for the alpha-galactopyranoside, and in the range of 9-39 s-1 within a temperature range of 5-25 degrees C for the beta-galactopyranoside. A considerable dissociation activation enthalpy of ca. 10 kcal mol-1 was found for both anomers. A two-step binding model, consistent with the present NMR data and with previous UV and CD spectroscopic data, is presented.
通过13C NMR研究了α-甲基-D-吡喃半乳糖苷和β-甲基-D-吡喃半乳糖苷与花生抗-T凝集素的结合动力学，使用在C-1处特异性富集13C的甲基吡喃半乳糖苷。报告了缔合和解离速率常数及其活化参数。α-吡喃半乳糖苷的缔合速率常数为4.6×10(4) M-1 s-1，β-吡喃半乳糖苷的缔合速率常数为3.6×10(4) M-1 s-1，比扩散控制过程预期的值低几个数量级。对于两种异头物，缔合速率常数与温度无关，这意味着缔合过程在没有显著活化焓的情况下发生。然而，发现两种配体都有相当大的缔合活化熵。α-吡喃半乳糖苷在5-35℃温度范围内的解离速率常数在9-46 s-1范围内，β-吡喃半乳糖苷在5-25℃温度范围内的解离速率常数在9-39 s-1范围内。两种异头物都发现了约10 kcal mol-1的相当大的解离活化焓。提出了一个与当前NMR数据以及先前的UV和CD光谱数据一致的两步结合模型。
