Studies were conducted on the depolymerization of polyadenylic acid (poly (A)) by RNAse A (EC 3.1.4.22) depending on the pH (pH 5-8). The results showed that depending on the pH, the ratio Vmax/Km was analogous to that described earlier for nucleoside-2', 3'-cyclophosphates and dinucleoside phosphates. This indicates that depolymerization of poly (A), transesterification and hydrolysis of specific substrates is achieved by the same ionizing groups of the enzyme with pKa 5.4 and pKb 6.4. The rate of degradation of poly (A) is also influenced by the state of adenine ionization, the protonation of which leads to the formation of a double helical poly (A), and does not serve as a substrate for RNAse A. The low rate for the depolymerization of poly (A) in the presence of RNAse A is related to a decrease in the turnover number of the enzyme, and an increase in the molecular weight of the enzyme (RNAse dimer), leads to a decrease in the Km, and does not effect Vmax. This indicates that the rate of depolymerization of polynucleotides is determined by orientation of factors. On the basis of the comparison of the resultant kinetic data, and the structure of the enzyme inhibitory complexes of RNAse S, which were studied by the method of x-ray structural analysis, a conclusion was reached on the kinetic characteristics of RNAse A specificity with respect to polymeric substrates, which is determined by the orinetation of the ribose phosphate relative to the catalytic groups of the active site.

中文翻译：

---

核糖核酸酶A解聚腺苷酸的动力学研究。

根据pH（pH 5-8），通过RNA酶A（EC 3.1.4.22）对聚腺苷酸（聚（A））解聚进行了研究。结果表明，取决于pH，比率Vmax / Km类似于先前针对核苷2'，3'-环磷酸盐和二核苷磷酸盐所描述的比率。这表明通过具有pKa 5.4和pKb 6.4的酶的相同电离基团可以实现聚（A）的解聚，特定底物的酯基转移和水解。聚腺苷酸的离子化状态也会影响聚腺苷酸的降解速度，其质子化会导致双螺旋聚腺苷酸A的形成，而不是RNAse A的底物。在RNA酶A存在下聚（A）的解聚反应与酶的周转次数减少有关，酶（RNAse二聚体）的分子量增加，导致Km降低，并且不影响Vmax。这表明多核苷酸的解聚速率是由因素的方向决定的。在比较所得动力学数据和通过X射线结构分析方法研究的RNA酶S的酶抑制复合物的结构的基础上，得出了RNA酶A特异性的动力学特征。对于聚合物底物而言，这取决于核糖磷酸酯相对于活性位点的催化基团的排列。这表明多核苷酸的解聚速率是由因素的方向决定的。在比较所得动力学数据和通过X射线结构分析方法研究的RNA酶S的酶抑制复合物的结构的基础上，得出了RNA酶A特异性的动力学特征。对于聚合物底物而言，这取决于核糖磷酸酯相对于活性位点的催化基团的排列。这表明多核苷酸的解聚速率是由因素的方向决定的。在比较所得动力学数据和通过X射线结构分析方法研究的RNA酶S的酶抑制复合物的结构的基础上，得出了RNA酶A特异性的动力学特征。对于聚合物底物而言，这是通过核糖磷酸酯相对于活性位点的催化基团的排列来确定的。