A kinetic comparison of cardiac glycoside interactions with Na+,K+-ATPases from skeletal and cardiac muscle and from kidney.
A kinetic comparison of cardiac glycoside interactions with Na+,K+-ATPases from skeletal and cardiac muscle and from kidney.
复制标题
强心苷与骨骼肌、心肌和肾脏的 Na,K-ATP 酶相互作用的动力学比较。
DOI：
10.1016/0003-9861(80)90448-8
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发表时间：
1980
影响因子：
3.9
通讯作者：
Schwartz,A
中科院分区：
文献类型：
--
作者：
Wallick,ET;Pitts,BJ;Lane,LK;Schwartz,A
测定了从狗骨骼肌、牛心肌和羔羊肾髓质分离的酶的[3 H]哇巴因与Na+，K+-ATP酶的结合率和酶-哇巴因复合物的解离率。的关联率的存在下，如镁，钠，钾，ATP和无机磷酸盐的配体的强烈影响。对于一组特定的结合配体，协会之间的研究三种酶的速率没有太大的变化，虽然骨骼肌酶是最快的。相反，解离速率相对独立的配体条件。不同酶源的解离速率也有很大差异，骨骼肌Na+，K+-ATP酶的解离速率最快。虽然Na+，K+-ATP酶对哇巴因的亲和力的主要决定因素是解离速率，但缔合速率也起作用。由于哇巴因在镁、ATP、钠和钾的存在下与Na+，K+-ATP酶的结合非常缓慢，因此难以获得哇巴因抑制水解活性的I 50（平衡）值。如果在长时间（3小时）后进行活性测量，则根据Na+，K+-ATP酶活性抑制估计的酶对哇巴因的亲和力接近根据[3 H]哇巴因结合计算的值。骨骼肌酶与心肌酶的I_（50）值之比与哇巴因的I_（50）值之比相同，表明哇巴因的糖部分与两种酶的受体相互作用。因此，很明显，骨骼肌Na+，K+-ATP酶中糖结合位点的缺失不是该酶解离速率较快的原因。
The rates of association of [3H]ouabain to Na+,K+-ATPase and the rates of dissociation of the enzyme-ouabain complexes were determined for enzymes isolated from dog skeletal muscle, beef heart muscle, and lamb kidney medulla. The rates of association were strongly influenced by the presence of ligands such as magnesium, sodium, potassium, ATP, and inorganic phosphate. For a particular set of binding ligands, the rates of association did not vary much amongst the three enzymes studied, although enzyme from skeletal muscle was the fastest. In contrast, the rates of dissociation were relatively independent of the ligand conditions. The rates of dissociation also varied greatly amongst the enzyme sources, with skeletal muscle Na+,K+-ATPase being the fastest. Although the major determinant of the affinity of the Na+,K+-ATPase for ouabain is the rate of dissociation, the rate of association also plays a role. Since the binding of ouabain to the Na+,K+-ATPase in the presence of magnesium, ATP, sodium, and potassium is very slow, it is difficult to obtain an I50(equilibrium) value for the inhibition of hydrolytic activity by ouabain. If measurements of activity are made after a long period of time (3 h), the affinity of the enzyme for ouabain, estimated from inhibition of Na+,K+-ATPase activity, approached the value calculated from [3H]ouabain binding. The ratio of the I50value for ouabagenin to that for ouabain for the skeletal muscle enzyme was the same as that for cardiac muscle enzyme, indicating that the sugar moiety of ouabain was interacting with the receptor of both enzymes. It is apparent, therefore, that the absence of a sugar binding site in skeletal Na+,K+-ATPase is not the reason for the faster dissociation rate of this enzyme.