Makimoto S, Taniguchi Y
Department of Chemistry, Faculty of Science and Engineering Ritsumeikan University, Kyoto, Japan.
Biochim Biophys Acta. 1988 Jun 13;954(3):343-6. doi: 10.1016/0167-4838(88)90089-1.
With and without p-chlorophenol as an activator, the rates of hydrolysis of p-nitrophenyl acetate catalyzed by alpha-chymotrypsin were measured at pressures up to 2 kbar at 25 degrees C. From the pressure dependence of the rate constant (kcat)A and (kcat)0 of the product formation with and without an activator, the activation volumes (delta V not equal to cat)A and (delta not equal to cat)0 were +2 and -6 +/- 1 cm3.mol-1. From the pressure dependence of the equilibrium constant (KA) of incorporation of p-chlorophenol into the enzyme, the volume change (delta VA) was -10 +/- 1 cm3.mol-1. The mechanisms of the substrate activation are discussed in terms of the activation and reaction volumes.
在有无对氯苯酚作为激活剂的情况下，于25℃、高达2千巴的压力下测定了α-胰凝乳蛋白酶催化乙酸对硝基苯酯的水解速率。根据有无激活剂时产物形成的速率常数(kcat)A和(kcat)0对压力的依赖性，激活体积(ΔV≠cat)A和(Δ≠cat)0分别为+2和-6±1 cm³·mol⁻¹。根据对氯苯酚掺入酶的平衡常数(KA)对压力的依赖性，体积变化(ΔVA)为-10±1 cm³·mol⁻¹。根据激活体积和反应体积讨论了底物激活的机制。
