胃（H⁺，K⁺）-ATP酶

Gastric (H+,K+)-ATPase.

作者信息

Soumarmon A, Lewin M J

出版信息

Biochimie. 1986 Dec;68(12):1287-91. doi: 10.1016/s0300-9084(86)80080-3.

Abstract

Gastric acid secretion results from the activity of a specific ATPase, the (H+,K+)-ATPase. This enzyme, discovered in 1973, exchanges H+ for K+. It has two ATP binding sites, both involved in enzyme activity, whose affinities vary as a function of the H+ and K+ concentrations. Hydrolysis of ATP at the highest affinity site leads to the synthesis of a covalent aspartyl phosphate which accumulates in the absence of K+. The presence of this cation accelerates dephosphorylation resulting in the stimulation of ATPase (and PNPPase) activity. The structure of membranous (H+,K+)-ATPase is poorly defined. n-Octylglucoside solubilizes an active enzyme of 390-420 kDa which can be partly depolymerized using cholate. The monomer, characterized in SDS has a 95 kDa molecular mass and is inactive. In the presence of magnesium, (H+,K+)-ATPase catalyzes the active and neutral exchange of H+ for K+ at the expense of ATP. In the absence of ATP, (H+,K+)-ATPase acts as a passive transporter exchanging K+ for K+ at maximal rate and H+ for K+ at a 20 times slower rate.

摘要

胃酸分泌源于一种特定的ATP酶即（H⁺，K⁺）-ATP酶的活性。这种酶于1973年被发现，可将H⁺与K⁺进行交换。它有两个ATP结合位点，二者均参与酶的活性，其亲和力随H⁺和K⁺浓度而变化。在亲和力最高的位点水解ATP会导致合成一种共价天冬氨酰磷酸，在没有K⁺的情况下该磷酸会积累。这种阳离子的存在会加速去磷酸化，从而刺激ATP酶（和对硝基苯磷酸酶）的活性。膜状（H⁺，K⁺）-ATP酶的结构尚不清楚。正辛基葡糖苷可溶解一种390 - 420 kDa的活性酶，该酶可用胆酸盐部分解聚。在SDS中表征的单体分子量为95 kDa且无活性。在镁存在的情况下，（H⁺，K⁺）-ATP酶以ATP为代价催化H⁺与K⁺的主动和中性交换。在没有ATP的情况下，（H⁺，K⁺）-ATP酶作为一种被动转运体，以最大速率将K⁺与K⁺进行交换，并以慢20倍的速率将H⁺与K⁺进行交换。