Subunit dissociation in the allosteric regulation of Glycerol kinase from Escherichia coli. 3. Role in desensitization.
Subunit dissociation in the allosteric regulation of Glycerol kinase from Escherichia coli. 3. Role in desensitization.
复制标题
大肠杆菌甘油激酶变构调节中的亚基解离。
作者：
J. de Riel;H. Paulus
甘油激酶对由盐、尿素和高pH引起的果糖1，6-二磷酸的变构抑制的脱敏机制已经根据早期论文[de Riel，J.K.，和Paulus H.（1978），Biochemistry 17]，涉及亚基解离和配体结合。KCl（0.4 M）导致四聚甘油激酶对果糖，1，6-二磷酸的亲和力降低10倍，但对解离过程本身没有显着影响。尿素（2 M）导致甘油激酶四聚体解离为二聚体的平衡常数大幅增加，但对四聚体对变构抑制剂的亲和力没有影响。高pH（9- 10）对亚基解离常数的影响很小，但大大降低了亚基缔合和解离的速率。因此，甘油激酶对变构抑制的脱敏可以通过三种不同的机制发生，其中两种机制与酶的多构性质直接相关。
The mechanism of desensitization of glycerol kinase to allosteric inhibition by fructose 1,6-bisphosphate caused by salt, urea, and high pH has been examined in the light of the model proposed in an earlier paper [de Riel, J. K., and Paulus H. (1978), Biochemistry 17] relating subunit dissociation and ligand binding. KCl (0.4 M) causes a tenfold decrease in the affinity of tetrameric glycerol kinase for fructose, 1,6-bisphosphate but has no significant effect on the dissociation process itself. Urea (2 M) causes a large increase in the equilibrium constant for the dissociation of the glycerol kinase tetramer to dimer but has no effect on the affinity of the tetramer for the allosteric inhibitor. High pH (9--10) has only a small effect on the subunit dissociation constant but greatly reduces the rates of subunit association and dissociation. Desensitization of glycerol kinase to allosteric inhibition can thus occur by three different mechanisms, two of which are directly related to the polysteric nature of the enzyme.