ATP及ATP类似物对钠钾ATP酶活性的加速作用。

The acceleration of Na+,K+-ATPase activity by ATP and ATP analogues.

作者信息

Suzuki K, Taniguchi K, Iida S

出版信息

J Biol Chem. 1987 Aug 25;262(24):11752-7.

Abstract

Since Na+,K+-ATPase (EC 3.6.1.3) of pig kidney modified with a fluorescent sulfhydryl reagent, N-[p-(2-benzimidazolyl) phenyl]maleimide, at Cys-964 of the alpha-chain showed ATP-dependent, reversible, and dynamic fluorescence changes (Nagai, M., Taniguchi, K., Kangawa, K., Matsuo, S., Nakamura, S., and Iida, S. (1986) J. Biol. Chem. 261, 13197-13202), we studied the conformational change during Na+,K+-ATPase reaction using the modified enzyme. The addition of K+ to the enzyme increased the fluorescence intensity to 2% in the presence of 160 mM Na+ and 3 mM Mg2+ (K0.5 = 16.4 mM). Addition of low concentrations of ATP immediately increased the intensity to 3.2% (K0.5 less than 0.1 microM) to accumulate fully K+-bound enzyme in the presence of 43 mM K+ with Na+ and Mg2+, but further addition of higher concentrations of ATP diminished the increase (K0.5 = 120 microM). After exhaustion of ATP, the fluorescence intensity decreased to -0.4% (K0.5 = 0.3 microM) and -2% (K0.5 = 20 microM), respectively, in the presence of low and high concentrations of ADP produced from ATP. High concentrations of ATP accelerated Na+,K+-ATPase activity with a simultaneous increase in the amount of ADP-sensitive phosphoenzyme irrespective of the modification. Adenylyl imidodiphosphate and ADP accelerated Na+,K+-ATPase activity in the presence of 2.7 microM ATP by decreasing the extent of the fluorescence without affecting the amount of phosphoenzyme, irrespective of the modification. These data suggest that Na+,K+-ATPase activity was accelerated due to the acceleration of the breakdown of K+-bound enzyme by high concentrations of ATP and ATP analogues.

摘要

由于用荧光巯基试剂N-[对-(2-苯并咪唑基)苯基]马来酰亚胺修饰猪肾的Na⁺,K⁺-ATP酶（EC 3.6.1.3），在α链的Cys-964处显示出ATP依赖性、可逆性和动态荧光变化（永井，M.，谷口，K.，神川，K.，松尾，S.，中村，S.，饭田，S.（1986年）《生物化学杂志》261，13197 - 13202），我们使用修饰后的酶研究了Na⁺,K⁺-ATP酶反应过程中的构象变化。在160 mM Na⁺和3 mM Mg²⁺存在下，向酶中添加K⁺使荧光强度增加2%（K₀.₅ = 16.4 mM）。添加低浓度的ATP会立即使强度增加到3.2%（K₀.₅小于0.1 μM），以便在43 mM K⁺与Na⁺和Mg²⁺存在时使完全结合K⁺的酶积累，但进一步添加更高浓度的ATP会使增加量减少（K₀.₅ = 120 μM）。ATP耗尽后，在由ATP产生的低浓度和高浓度ADP存在下，荧光强度分别降至-0.4%（K₀.₅ = 0.3 μM）和-2%（K₀.₅ = 20 μM）。高浓度的ATP加速了Na⁺,K⁺-ATP酶活性，同时增加了ADP敏感磷酸酶的量，与修饰无关。腺苷酰亚胺二磷酸和ADP在2.7 μM ATP存在下通过降低荧光程度加速了Na⁺,K⁺-ATP酶活性，而不影响磷酸酶的量，与修饰无关。这些数据表明，Na⁺,K⁺-ATP酶活性的加速是由于高浓度的ATP和ATP类似物加速了结合K⁺的酶的分解。