BINDING OF OXIDIZED COENZYMES BY GLUTAMATE DEHYDROGENASE AND EFFECTS OF GLUTARATE AND PURINE NUCLEOTIDES
BINDING OF OXIDIZED COENZYMES BY GLUTAMATE DEHYDROGENASE AND EFFECTS OF GLUTARATE AND PURINE NUCLEOTIDES
复制标题
DOI：
10.1042/bj1260975
复制
发表时间：
1972-01-01
影响因子：
4.1
通讯作者：
EGAN, RR
中科院分区：
文献类型：
--
作者：
DALZIEL, K;EGAN, RR
1. 通过平衡透析，在磷酸钠缓冲液（pH7.0）中研究了 NAD+ 和 NADP+ 与谷氨酸脱氢酶的结合。解离常数的近似值分别为 0.47 和 2.5mm。对于 NAD+，该值与初始速率结果估计的值一致。 2. 在底物类似物戊二酸存在的情况下，两种辅酶结合得更牢固，并且每个酶亚基有一个活性中心。结合结果不能用独立且相同的活性中心来描述，并且低辅酶浓度下的结合比高浓度下的结合更强。寡聚物的六个亚基不相同，或者它们之间在辅酶与戊二酸三元复合物的结合中存在负相互作用。后一种解释受到青睐。 3. 结合研究支持了早期谷氨酸反应动力学研究得出的结论。 4. 在有或没有戊二酸的情况下，ADP 和 GTP 分别降低和增加酶对 NAD+ 和 NADP+ 的亲和力。 ADP 消除了戊二酸存在下的负结合相互作用，从而降低了低浓度辅酶对辅酶的亲和力。 5、在戊二酸、GTP和NAD+或NADP+存在下，酶寡聚体的缔合被阻止，酶的溶解度下降；酶和配体的复合物很容易结晶。 6. 结合早期动力学研究对结果进行了讨论。
1. The binding of NAD+and NADP+to glutamate dehydrogenase has been studied in sodium phosphate buffer, pH7.0, by equilibrium dialysis. Approximate values for the dissociation constants are 0.47 and 2.5mmrespectively. For NAD+the value agrees with that estimated from initial-rate results. 2. In the presence of the substrate analogue glutarate both coenzymes are bound more firmly, and there is one active centre per enzyme subunit. The binding results cannot be described in terms of independent and identical active centres, and binding is stronger at low coenzyme concentrations than at high concentrations. Either the six subunits of the oligomer are not identical or there are negative interactions between them in the binding of coenzymes in ternary complexes with glutarate. The latter explanation is favoured. 3. The binding studies support the conclusions drawn from earlier kinetic studies of the glutamate reaction. 4. ADP and GTP respectively decrease and increase the affinity of the enzyme for NAD+and NADP+, in both the presence and absence of glutarate. The negative binding interactions in the presence of glutarate are abolished by ADP, which decreases the affinity for the coenzymes at low concentrations of the latter. 5. In the presence of glutarate, GTP and NAD+or NADP+, the association of enzyme oligomers is prevented, and the solubility of the enzyme is decreased; the complex of enzyme and ligands readily crystallizes. 6. The results are discussed in relation to earlier kinetic studies.