Reenstra W W, Forte J G
J Membr Biol. 1981;61(1):55-60. doi: 10.1007/BF01870752.
The initial rate of ATP-dependent proton uptake by hog gastric vesicles was measured at pH's between 6.1 and 6.9 by measuring the loss of protons from the external space with a glass electrode. The apparent rates of proton loss were corrected for scalar proton production due to ATP hydrolysis. For vesicles in 150 mM KCl and pH 6.1, corrected rates of proton uptake and ATP hydrolysis were 639 +/- 84 and 619 +/- 65 nmol/min x mg protein, respectively, giving an H+/ATP ratio of 1.03 +/- .07. Furthermore, at all pH's tested the ratio of the rate of proton uptake to the rate of ATP hydrolysis was not significantly different than 1.0. No proton uptake (less than 10 nmol/min x mg protein) was exhibited by vesicles in 159 mM NaCl at pH 6.1 despite ATP hydrolysis of 187 +/- 46 nmol/min x mg (nonproductive hydrolysis). Comparison of the rates of proton transport and ATP hydrolysis in various mixture of KCl and NaCl showed that the H+/ATP stoichiometries were not significantly different than 1.0 at all concentrations of K+ greater than 10 mM. This fact suggests that the nonproductive rate is vanishingly small at these concentrations, implying that the measured H+/ATP stoichiometry is equal to the enzymatic stoichiometry. This result shows that the isolated gastric (K+ + H+)-ATPase is thermodynamically capable of forming the observed proton gradient of the stomach.
通过用玻璃电极测量外部空间质子的损失，在pH值6.1至6.9之间测定了猪胃小泡依赖ATP的质子摄取初始速率。对由于ATP水解产生的标量质子进行校正后得到表观质子损失速率。对于处于150 mM KCl和pH 6.1的小泡，校正后的质子摄取速率和ATP水解速率分别为639±84和619±65 nmol/min·mg蛋白质，H⁺/ATP比值为1.03±0.07。此外，在所有测试的pH值下，质子摄取速率与ATP水解速率的比值与1.0没有显著差异。在pH 6.1的159 mM NaCl中，尽管ATP水解速率为187±46 nmol/min·mg（无效水解），小泡仍未表现出质子摄取（小于10 nmol/min·mg蛋白质）。在KCl和NaCl的各种混合物中比较质子运输速率和ATP水解速率表明，在所有K⁺浓度大于10 mM时，H⁺/ATP化学计量比与1.0没有显著差异。这一事实表明，在这些浓度下无效速率极小，这意味着测得的H⁺/ATP化学计量比等于酶促化学计量比。该结果表明，分离出的胃（K⁺+H⁺）-ATP酶在热力学上能够形成观察到的胃质子梯度。
