Beck C F, Eisenhardt A R, Neuhard J
J Biol Chem. 1975 Jan 25;250(2):609-16.
Deoxycytidine triphosphate deaminase (EC 3.5.4., dCTP aminohydrolase) of Salmonella typhimurium LT2 has been pruified 500-fold. The reaction requires the presence of Mg-2plus, Mn-2plus, Ca-2lus, or Co-2plus. Kinetics of the reaction with varying Mg-2plus concentrations, keeping the concentration of dCTP constant, suggests that the true substrate of the reaction is MgdCTP. The dependence of the rate of reaction on dCTP concentration in the presnece of 5-fold excess of Mg-2plus is sigmoid, with a Hill coefficient of 1.7. The enzyme is specifically inhibited by dTTP and dUTP. In the presence of increasing dTTP concentrations the sigmoidicity of the substrate saturation curves increases. With 0.2 and 0.4 mM dTTP the Hill coefficients are 2.6 and 3.0, respectively. Despite several attempts no dissociation of the substrate site and the inhibitor site of the enzyme was achieved.
鼠伤寒沙门氏菌LT2的脱氧胞苷三磷酸脱氨酶（EC 3.5.4.，dCTP氨基水解酶）已被纯化了500倍。该反应需要Mg²⁺、Mn²⁺、Ca²⁺或Co²⁺的存在。在保持dCTP浓度恒定的情况下，研究不同Mg²⁺浓度下反应的动力学，结果表明该反应的真正底物是MgdCTP。在Mg²⁺过量5倍的情况下，反应速率对dCTP浓度的依赖性呈S形，希尔系数为1.7。该酶受到dTTP和dUTP的特异性抑制。随着dTTP浓度的增加，底物饱和曲线的S形程度增加。在0.2 mM和0.4 mM dTTP存在时，希尔系数分别为2.6和3.0。尽管进行了多次尝试，但均未实现该酶底物位点和抑制剂位点的解离。
