Deschrevel B, Vincent J C, Thellier M
Laboratoire Polymères, Biopolymères, Membranes, URA 500 CNRS, Université de Rouen, Mont Saint Aignan, France.
Arch Biochem Biophys. 1993 Jul;304(1):45-52. doi: 10.1006/abbi.1993.1319.
We have studied the hydrolysis and synthesis reactions of the peptide bond involved in N-Cbz-L-tryptophanyl-glycineamide as catalyzed by alpha-chymotrypsin in various mixtures of water and 1,4-butanediol. Using a constant nonsaturating concentration of substrate, the initial reaction rates decreased exponentially with decreasing water content in the solvent mixture. When the water content was decreased from 100 to 20% (v/v), the maximum rate of reaction did not vary by more than a factor of 2 to 4, whereas the Michaelis constant increased exponentially. This exponential variation of the Michaelis constant was due to changes in the partitioning of the substrate between the active site of the enzyme and the solvent. In these processes, the actual rate constants did not vary when the relative contents of water and 1,4-butanediol were varied.
我们研究了在水和1,4 - 丁二醇的各种混合物中，α-胰凝乳蛋白酶催化N - Cbz - L - 色氨酰 - 甘氨酰胺中肽键的水解和合成反应。使用恒定的非饱和底物浓度，随着溶剂混合物中水含量的降低，初始反应速率呈指数下降。当水含量从100%降至20%（v/v）时，最大反应速率的变化不超过2至4倍，而米氏常数呈指数增加。米氏常数的这种指数变化是由于底物在酶的活性位点和溶剂之间的分配变化所致。在这些过程中，当水和1,4 - 丁二醇的相对含量变化时，实际速率常数并未改变。
