Reactivity of gastric (H+ + K+)-ATPase to N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline.
The K+-dependent ATPase and p-nitrophenyl phosphatase activity of, and formation of phosphoenzyme by, hog parietal cell membranes were inhibited in a time- and concentration-dependent manner by the carboxyl-activating reagent, N-ethoxycarbonyl-2-ethoxy-1,2-dihydroquinoline (EEDQ). The kinetics of inactivation was pseudo first order and was similar to the EEDQ-catalyzed incorporation of [14C]glycine ethyl ester. The most likely mechanism is the EEDQ-dependent formation of inter- and intramolecular amide bonds. Cross-linking between the subunits of the ATPase occurs with EEDQ treatment. The presence of K+ on the luminal face of the enzyme is able to prevent EEDQ inhibition of K+ ATPase activity (but not intermolecular cross-linking), whereas ATP enhanced the rate of inactivation. EEDQ reaction with the enzyme therefore allows investigation of K+- and ATP-dependent states of the enzyme.
D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D002462:Cell Membrane / Q000201:enzymology; D005753:Gastric Mucosa / Q000201:enzymology*; D017506:H(+)-K(+)-Exchanging ATPase; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008274:Magnesium / Q000494:pharmacology; D015636:Magnesium Chloride; D011804:Quinolines / Q000494:pharmacology*; D012265:Ribonucleotides / Q000494:pharmacology; D013552:Swine
D000317:Adrenergic alpha-Antagonists; D011804:Quinolines; D012265:Ribonucleotides; D015636:Magnesium Chloride; C000470:EEDQ; D000251:Adenosine Triphosphatases; D017506:H(+)-K(+)-Exchanging ATPase; D008274:Magnesium