锌在细菌α-淀粉酶二聚体形式稳定中的作用。
The role of zinc in the stabilization of the dimeric form of bacterial alpha-amylase.
作者信息
Tellam R, Winzor D J, Nichol L W
出版信息
Biochem J. 1978 Jul 1;173(1):185-90. doi: 10.1042/bj1730185.
Bacterial alpha-amylase was shown by equilibrium and velocity-sedimentation studies to be a monomer-dimer equilibrium system in 0.10M-NaCl/0.015M-calcium acetate/0.010M-EDTA, pH7.0; an association constant of 2.4 X 10(3)M-1 is obtained. Studies of the binding of Zn2+ to alpha-amylase in 0.10M-NaCl/0.005M-calcium acetate, pH7.0, yielded binding curves that exhibit dependence on the concentration of alpha-amylase (Zn2+-free) used in the equilibrium-dialysis experiments. Results are described very satisfactorily by a reaction scheme in which Zn2+ binds exclusively to the dimer of the above monomer--dimer system with an association constant of 1.0 X 10(6)M-1. The present results refute the earlier scheme for dimer stabilization by Zn2+ in which the metal ion formed a cross-link between two non polymerizing monomer units.
通过平衡和速度沉降研究表明，在0.10M氯化钠/0.015M醋酸钙/0.010M乙二胺四乙酸（pH7.0）中，细菌α-淀粉酶是一个单体-二聚体平衡体系；得到的缔合常数为2.4×10³M⁻¹。在0.10M氯化钠/0.005M醋酸钙（pH7.0）中对锌离子与α-淀粉酶结合的研究产生了结合曲线，该曲线显示出对平衡透析实验中使用的（无锌离子的）α-淀粉酶浓度的依赖性。通过一个反应方案可以非常令人满意地描述这些结果，在该方案中，锌离子仅与上述单体-二聚体体系的二聚体结合，缔合常数为1.0×10⁶M⁻¹。目前的结果反驳了早期锌离子使二聚体稳定的方案，在该方案中金属离子在两个非聚合单体单元之间形成交联。
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