Smith G S, Scholes P B
Biochim Biophys Acta. 1982 Jun 28;688(3):803-7. doi: 10.1016/0005-2736(82)90295-4.
Gastric microsomal vesicles isolated from dog fundic mucosa were shown to be relatively ion tight and have a low level of proton permeability. The H+ translocase, basal ATPase and K+-activated ATPase activities of these vesicles were measured and the H+/ATP stoichiometry calculated using either the total K+-ATPase or the K+-stimulatable component (total K+-ATPase--basal ATPase). The former estimations consistently gave stoichiometric of approximately one, whereas the use of only the K+-stimulatable component gave widely differing values. Measurement of the dephosphorylation of the enzyme under basal conditions revealed both a labile and a stable phosphoenzyme component. The rate of decay of the labile component completely accounted for the basal ATPase activity observed. We conclude that the basal ATPase associated with our preparations is a spontaneous dephosphorylation of the phosphoenzyme occurring in the absence of K+ and that the H+/ATP stoichiometry of the gastric ATPase is one.
从犬胃底黏膜分离出的胃微粒体囊泡显示出相对离子紧密性，且质子通透性较低。对这些囊泡的H⁺转运酶、基础ATP酶和K⁺激活的ATP酶活性进行了测定，并使用总K⁺ - ATP酶或K⁺刺激成分（总K⁺ - ATP酶 - 基础ATP酶）计算H⁺/ATP化学计量比。前者的估计值始终约为1，而仅使用K⁺刺激成分则得出差异很大的值。在基础条件下对酶的去磷酸化进行测量，发现了一种不稳定和一种稳定的磷酸酶成分。不稳定成分的衰减速率完全解释了所观察到的基础ATP酶活性。我们得出结论，与我们的制剂相关的基础ATP酶是在没有K⁺的情况下发生的磷酸酶的自发去磷酸化，并且胃ATP酶的H⁺/ATP化学计量比为1。
