Murakami K, Iwata S, Haneda M, Yoshino M
Department of Biochemistry, Aichi Medical University, Japan.
Biometals. 1997 Jul;10(3):169-74. doi: 10.1023/a:1018395510334.
The regulatory role of divalent metal cations in the NADP-linked isocitrate dehydrogenase (EC 1.1.1.42) from porcine heart was analysed. Saturation curves with respect to the substrate threo-DS-isocitrate complexed with the metals including manganous, cadmium, cobaltous and zinc ions showed sigmoid relationships characteristic of allosteric enzymes. The Hill's interaction coefficients were 1.90, 1.75, 1.28 and 1.12, respectively. Saturation kinetics of the substrate-metal complexes including magnesium, ferrous and nickel ions exhibited normal hyperbolic curves with Hill's coefficients of 1. The ionic radii of metal cations were closely correlated with the maximal velocity, the enzyme affinity and the Hill's n11 values for the substrate-metal complexes. Cooperative interactions of metal-substrate complexes with NADP-isocitrate dehydrogenase are discussed in relation to the sites of the enzyme for the binding of the metal-substrate complex.
分析了二价金属阳离子在猪心NADP连接的异柠檬酸脱氢酶（EC 1.1.1.42）中的调节作用。以与包括锰、镉、钴和锌离子在内的金属络合的底物苏糖-DS-异柠檬酸绘制的饱和曲线显示出别构酶特有的S形关系。希尔相互作用系数分别为1.90、1.75、1.28和1.12。包括镁、亚铁和镍离子在内的底物-金属络合物的饱和动力学表现出正常的双曲线，希尔系数为1。金属阳离子的离子半径与底物-金属络合物的最大速度、酶亲和力和希尔n11值密切相关。结合金属-底物复合物与NADP-异柠檬酸脱氢酶的协同相互作用，讨论了该酶结合金属-底物复合物的位点。
