DUAL NUCLEOTIDE SPECIFICITY OF BOVINE GLUTAMATE-DEHYDROGENASE - THE ROLE OF NEGATIVE CO-OPERATIVITY
DUAL NUCLEOTIDE SPECIFICITY OF BOVINE GLUTAMATE-DEHYDROGENASE - THE ROLE OF NEGATIVE CO-OPERATIVITY
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DOI：
10.1042/bj1910299
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发表时间：
1980-01-01
影响因子：
4.1
通讯作者：
BELL, JE
中科院分区：
文献类型：
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作者：
ALEX, S;BELL, JE
NAD+和NADP+的硫代烟酰胺类似物是牛谷氨酸脱氢酶的良好替代辅酶，具有相似的亲和力和亲和力。40%的天然辅酶获得的Kmax。两种硫代烟酰胺类似物均显示非线性Lineweaver-Burk图，其与天然辅酶归因于负协同性。由于还原的硫代烟酰胺类似物在340 nm处具有等吸光点，在400 nm处具有最大吸收，因此可以通过双波长光谱法同时监测天然辅酶和硫代烟酰胺类似物的还原。当谷氨酸脱氢酶与NAD+和硫代-NADP+同时存在时，酶寡聚体感测其辅酶结合位点的饱和，而不管辅酶的确切性质，并且即使当存在低饱和度的监测辅酶时，也将寡聚体锁定为其高度饱和的形式。这些实验证实了谷氨酸脱氢酶在其催化活性形式下显示负协同性的建议。
The thionicotinamide analogues of NAD+ and NADP+ were good alternative coenzymes for bovine glutamate dehydrogenase, with similar affinity and .apprx. 40% of the Kmax obtained with the natural coenzymes. Both thionicotinamide analogues show non-linear Lineweaver-Burk plots, which with the natural coenzymes were attributed to negative cooperativity. Since the reduced thionicotinamide analogues have an isosbestic point at 340 nm and have an absorption maximum at 400 nm, it is possible to monitor reduction of natural coenzyme and thionicotinamide analogue simultaneously by dual-wavelength spectroscopy. When glutamate dehydrogenase is presented with NAD+ and thio-NADP+ simultaneously, the enzyme oligomer senses saturation of its coenzyme-binding sites irrespective of the exact nature of the coenzyme and locks the oligomer into its highly saturated form even when low saturation of the monitored coenzyme is present. These experiments substantiate the suggestion that glutamate dehydrogenase shows negative cooperativity in its catalytically active form.