Neumann H, Kezdy F, Hsu J, Rosenberg I H
Biochim Biophys Acta. 1975 Jun 24;391(2):292-300. doi: 10.1016/0005-2744(75)90253-3.
The effect of tris (hydroxymethyl) aminomethane concentrations on the rate of calf intestinal alkaline phosphatase-catalyzed hydrolysis of p-nitrophenyl phosphate was studied, in the pH range 8-10, where no transphosphorylation reaction could be detected. Kinetic analysis of the results permitted description of the effect of Tris concentrations T on the rate of enzyme catalyzed hydrolysis (V) by the following equation: (see article). The rate-accelerating effect of Tris concentrations can be ascribed to two different mechanisms: At moderate Tris concentrations (0.01-0.20 M) the enzyme forms a reversible addition complex with a Tris molecule. This complex has an enhanced catalytic activity. We suggest that the binding of Tris to the enzyme could potentiate a second active site of the enzyme, due to its ionization effect upon an acidic group of the enzyme of pK = 8.9. The modest linear rate accelerating effect of Tris at high concentrations (0.20-0.60 M) could be ascribed to the change of the dielectric constant of the medium, the degree of solvation of the protein, or change in the tertiary structure of the enzyme.
研究了在pH值8 - 10范围内（在此范围内未检测到转磷酸化反应），三（羟甲基）氨基甲烷浓度对小牛肠碱性磷酸酶催化对硝基苯磷酸酯水解速率的影响。对结果进行动力学分析后，可用以下方程描述三羟甲基氨基甲烷浓度（T）对酶催化水解速率（V）的影响：（见文章）。三羟甲基氨基甲烷浓度的速率加速效应可归因于两种不同机制：在中等三羟甲基氨基甲烷浓度（0.01 - 0.20 M）下，酶与一个三羟甲基氨基甲烷分子形成可逆加成复合物。该复合物具有增强的催化活性。我们认为，由于三羟甲基氨基甲烷对pK = 8.9的酶酸性基团的电离作用，它与酶的结合可能增强了酶的第二个活性位点。在高浓度（0.20 - 0.60 M）下，三羟甲基氨基甲烷适度的线性速率加速效应可归因于介质介电常数的变化、蛋白质的溶剂化程度或酶三级结构的变化。
