Feltch S M, Stuehr J E
Biochemistry. 1979 May 15;18(10):2000-4. doi: 10.1021/bi00577a024.
Temperature-jump relaxation studies in deoxy-ribonuclease I were carried out at 10 degrees C and [I] = 0.1 M. The single observed relaxation time, which varied from 10(-4) to 10(-5) s, was characterized as a function of enzyme concentration, pH, and indicator concentration. The concentration and pH dependences of the relaxation time are in quantitative agreement with a mechanism involving an isomerization of the enzyme coupled to a rapid proton ionization process. The best fit forward and reverse isomerization rate constants are 6.5 X 10(3) and 7.2 X 10(4) s-1, respectively; the apparent pK is 5.7. The addition of urea brought about reductions in both the amplitude of the relaxation effect and the enzyme activity.
在10℃和[I]=0.1M条件下对脱氧核糖核酸酶I进行了温度跃变弛豫研究。观察到的单一弛豫时间在10⁻⁴至10⁻⁵秒之间变化，该弛豫时间作为酶浓度、pH值和指示剂浓度的函数进行了表征。弛豫时间对浓度和pH值的依赖性与一种涉及酶异构化并与快速质子电离过程耦合的机制在定量上是一致的。最佳拟合的正向和反向异构化速率常数分别为6.5×10³和7.2×10⁴s⁻¹；表观pK为5.7。添加尿素导致弛豫效应的幅度和酶活性均降低。
