钾离子激活的胰腺胰岛细胞膜中对硝基苯磷酸酯的水解作用
Potassium ion-activated hydrolysis of p-nitrophenyl phosphate in pancreatic islet-cell membranes.
作者信息
Lernmark A, Parman A, Täljedal I B
出版信息
Biochem J. 1977 Aug 15;166(2):181-7. doi: 10.1042/bj1660181.
Hydrolysis of p-nitrophenyl phosphate was measured in a fraction enriched in plasma membranes from pancreatic islets of non-inbred ob/ob mice. Hydrolysis was stimulated by K+ (10mM) in the pH range 5--10; a small peak of K+-induced activation was observed between pH7.5 and 8. Both the K+-induced activation and the hydrolysis in the absence of K+ were Mg2+-dependent; maximum activation was obtained with 10mM-K+ plus 5 mM-Mg2+. Rb+ was as effective an activator as K+. Ouabain was inhibitory, the effect being inversely related to the K+ concentration; 0.1--0.2mM-ouabain caused about 50% inhibition in the presence of 1 mM-K+, but had no demonstrable effect in the presence of 4--5mM-K+. The K+-stimulated activity was markedly inhibited by 0.1mM-ATP, 35--140 MM-Na+, or 0.01 mM-p-chloromercuribenzenesulphonic acid. Similarities to Rb+ accumulation suggest that catalysis of univalent cation flow in pancreatic beta-cells may be coupled to a phosphoryl-transfer reaction with ATP as natural substrate or regulator.
在来自非近交系ob/ob小鼠胰岛的富含质膜的组分中测定了对硝基苯磷酸酯的水解。在pH值5 - 10范围内，K⁺（10mM）可刺激水解；在pH7.5至8之间观察到K⁺诱导的活化的一个小峰值。K⁺诱导的活化和无K⁺时的水解均依赖于Mg²⁺；在10mM - K⁺加5mM - Mg²⁺时可获得最大活化。Rb⁺作为活化剂与K⁺一样有效。哇巴因具有抑制作用，其作用与K⁺浓度呈负相关；在存在1mM - K⁺时，0.1 - 0.2mM哇巴因引起约50%的抑制，但在存在4 - 5mM - K⁺时没有明显作用。K⁺刺激的活性被0.1mM - ATP、35 - 140μM - Na⁺或0.01mM - 对氯汞苯磺酸显著抑制。与Rb⁺积累的相似性表明，胰腺β细胞中单价阳离子流动的催化可能与以ATP作为天然底物或调节剂的磷酰转移反应偶联。
Zotero 插件