Two classes of site for ATP in the Ca2+-ATPase from human red cell membranes.
Two classes of site for ATP in the Ca2+-ATPase from human red cell membranes.
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人红细胞膜 Ca2-ATP 酶中 ATP 的两类位点。
DOI：
10.1016/0005-2736(78)90313-9
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发表时间：
1978
期刊：
影响因子：
--
通讯作者：
P. J. Garrahan
中科院分区：
文献类型：
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作者：
D. Richards;A. F. Rega;P. J. Garrahan
(1)人红细胞ca2 +-ATP酶活性对ATP浓度的响应可以用两条Michaelislike曲线的和来表示，一条K m为2.5 μM，另一条K m为145 μM。2.(2)较低K时ca2 +-ATP酶活性的最大值约为非极限ATP浓度时的10%。3.(3)在没有Mg +的情况下，ca2 +- atp酶活性仍保持30-50%。mg2 +增加了V和ca2 +的最大作用，但对ATP和ca2 +的表观亲和力没有影响。4.(4) ca2 +- atp酶活性的大幅增加是由于占据了较高的K - m位点，只有当Mg +存在时才会发生。5.(5)结果与来自人细胞膜的ca2 +-ATP酶具有两类ATP结合位点的观点一致，当酶以最大速率催化ATP水解时，这两类位点都被占据。6.(6)高亲和力位点的性质表明这是ca2 +- atp酶的催化位点。有人提出ATP在低亲和力位点的结合调节了系统的周转。
(1) The response of the Ca 2+-ATPase activity from human red cell membranes to ATP concentrations can be represented by the sum of two Michaelislike curves: one with a K m of 2.5 μM and the other with a K m of 145 μM. 2.(2) The maximum Ca 2+-ATPase activity elicited by occupation of the site with lower K m represents about 10% of the activity attainable at non-limiting ATP concentrations. 3.(3) 30–50% of the Ca 2+-ATPase activity with lower K m remains in the absence of Mg 2+. Mg 2+ increases V and the maximum effect of Ca 2+, having no effect on the apparent affinities for ATP and Ca 2+. 4.(4) The large increase in Ca 2+-ATPase activity which results from the occupation of the site with higher K m only takes place when Mg 2+ is present. 5.(5) Results are compatible with the idea that the Ca 2+-ATPase from human red cell membranes has two classes of site for ATP binding, both of which are occupied when the enzyme catalyzes the hydrolysis of ATP at maximum rate. 6.(6) The properties of the high affinity site suggest that this is the catalytic site of the Ca 2+-ATPase. It is proposed that binding of ATP at the low affinity site regulates the turnover of the system.