MECHANISM FOR CD-2+ INHIBITION OF (K+ + MG-2+)ATPASE ACTIVITY AND K+(RB-86+) UPTAKE JOIN ROOTS OF SUGAR-BEET (BETA-VULGARIS)
MECHANISM FOR CD-2+ INHIBITION OF (K+ + MG-2+)ATPASE ACTIVITY AND K+(RB-86+) UPTAKE JOIN ROOTS OF SUGAR-BEET (BETA-VULGARIS)
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DOI：
10.1111/j.1399-3054.1985.tb01900.x
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发表时间：
1985-01-01
影响因子：
6.4
通讯作者：
WINGSTRAND, G
中科院分区：
文献类型：
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作者：
LINDBERG, S;WINGSTRAND, G
采用稳态动力学研究了 Cd2+ 对甜菜根 (Beta vulgarisL. cv. Monohill) 膜结合 ATP 酶 K+ 刺激的影响，以及对完整或切除的甜菜根中 K+(86Rb+) 吸收的影响。研究了 Cd2+ 对 (Na++K++Mg2+)ATPase 的 12000–25000 g 根部分以及通过水性聚合物两相系统进一步纯化的 ATPase 的体外影响。观察到的数据可总结如下： 1) 高浓度（>100 μM）的 Cd2+ 以竞争性方式抑制 MgATPase 活性，可能是通过与 ATP 形成复合物。 2) Cd2+ 浓度 <100 μM 抑制高和低 K+ 亲和力位点的特异性 K+ 激活。两种不同纯度的 ATP 酶制剂的抑制模式似乎相同。在存在底物 MgATP 且 K+<5 mM 的情况下，Cd2+ 对 K+ 的抑制是非竞争性的。在 MgATP 和 K+>10 μM 存在的情况下，Cd2+ 的抑制是竞争性的。 3) 在低浓度 K+ 下，Cd2+ 还会抑制离体根和完整植物根中 2,4-二硝基苯酚 (DNP) 敏感（代谢）K+(86Rb+) 的吸收，但没有竞争性。 4) DNP 不敏感（非代谢）K+(86Rb+) 吸收受 Cd2+ 影响很小。由于 Cd2+ 在低浓度 K+ 下以相同的方式抑制 K+(86Rb+) 的代谢摄取和 ATP 酶的 K+ 激活，因此可能涉及相同的结合位点。因此，在田间条件下，当 K+ 浓度较低时，Cd2+ 的存在可能是不利的。
Steady state kinetics were used to examine the influence of Cd2+both on K+stimulation of a membrane‐bound ATPase from sugar beet roots (Beta vulgarisL. cv. Monohill) and on K+(86Rb+) uptake in intact or excised beet roots. The in vitro effect of Cd2+was studied both on a 12000–25000 g root fraction of the (Na++K++Mg2+)ATPase and on the ATPase when further purified by an aqueous polymer two‐phase system. The observed data can be summarized as follows: 1) Cd2+at high concentrations (>100 μM) inhibits the MgATPase activity in a competitive way, probably by forming a complex with ATP. 2) Cd2+at concentrations <100 μMinhibits the specific K+activation at both high and low affinity sites for K+. The inhibition pattern appears to be the same in the two ATPase preparations of different purity. In the presence of the substrate MgATP, and at K+<5 mM, the inhibition by Cd2+with respect to K+is uncompetitive. In the presence of MgATP and K+>10 μM, the inhibition by Cd2+is competitive. 3) At the low concentrations of K+, Cd2+also inhibits the 2,4‐dinitrophenol(DNP)‐sensitive (metabolic) K+(86Rb+) uptake uncompetitively both in excised roots and in roots of intact plants. 4) The DNP‐insensitive (non metabolic) K+(86Rb+) uptake is little influenced by Cd2+. As Cd2+inhibits the metabolic uptake of K+(86Rb+) and the K+activation of the ATPase in the same way at low concentrations of K+, the same binding site is probably involved. Therefore, under field conditions, when the concentration of K+is low, the presence of Cd2+could be disadvantageous.