Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P20020 (adenosine triphosphatase)
 3,299 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We employed a modification of our previously reported cerium-based cytochemical method for ouabain-sensitive, K-dependent p-nitrophenylphosphatase (Na-K ATPase) activity to detect ouabain-insensitive, K-stimulated p-nitrophenylphosphatase (K-pNPPase) activity in rat gastric glands. Biochemically, the enzyme activity of gastric glands incubated in a medium containing 50 mM Tricine buffer (pH 7.5), 50 mM KCl, 10 mM MgCl2, 2 mM CeCl3, 2 mM p-nitrophenylphosphate (pNPP), 2.5 mM levamisole, 10 mM ouabain, and 0.00015% Triton X-100, was optimal at pH 7.5-8.0 and decreased above pH 8.5. The amount of p-nitrophenol after incubation increased linearly in proportion to the amount of tissue in the medium. The enzyme activity was inhibited by omeprazole, sodium flouride (NaF), N-ethylmaleimide (NEM), and dicyclohexylcarbodiimide (DCCD). Heat-treated specimens had no enzyme activity. The enzyme activity increased with addition of K ions up to the concentration of 50 mM, and became constant above 50 mM. Cytochemically, the parietal cells of the gastric glands reacted positively for ouabain-insensitive K-pNPPase activity. Intense reaction was observed at the microvilli of the luminal surface and the intracellular canaliculi. The tubulovesicular system showed weak enzyme activity. The reaction products were found as fine, granular, electron-dense deposits in the cytoplasm just beneath the plasma membrane. The ouabain-insensitive K-pNPPase activity detected in this study appears, therefore, to be associated with that of H-transporting, K-stimulated adenosine triphosphatase (H-K ATPase).
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PMID:Detection of ouabain-insensitive H(+)-transporting, K(+)-stimulated p-nitrophenylphosphatase activity in rat gastric glands by cerium-based cytochemistry. 217 37

Enzyme activity that represents ouabain-insensitive, potassium-dependent p-nitrophenylphosphatase (p-NPPase) was assessed in rat atrial myocytes by biochemical and cytochemical procedures. No activity was detected in parallel experiments with ventricular myocytes. Fixed tissues were incubated in a reaction medium containing Tricine buffer, p-nitrophenylphosphate (p-NPP), KCl, MgCl2, CaCl2, CeCl3. Triton X-100, levamisole, and ouabain. Final pH was adjusted to 7.5. Biochemical studies showed that accumulation of p-nitrophenol in the medium was increased proportionally in accordance with the amount of incubated tissue. This activity was optimal with incubation at pH 7.5 and in the presence of KCl. Approximately 70% of the enzyme was inhibited by 2 mM CeCl3. Electron microscopic observations revealed reaction product (RP) at sites of ouabain-insensitive, potassium-dependent p-NPPase activity as electron-dense precipitate localized at the inner surface of the plasma membrane and at the T-tubules of atrial myocytes. Control experiments indicated that the activity was strongly inhibited by sodium orthovanadate and was repressed by omeprazole and 1,3-dicyclohexylcarbodiimide. X-ray microanalysis confirmed the presence of cerium within the cytochemical RP. The ouabain-insensitive, K-dependent p-NPPase activity detected in the present study is considered to be an isoform of a P-type, H-transporting, K-dependent adenosine triphosphatase (H,K-ATPase).
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PMID:Biochemical properties and cytochemical localization of ouabain-insensitive, potassium-dependent p-nitrophenylphosphatase activity in rat atrial myocytes. 901 8