Mechanism of the inhibition of hog gastric H+,K(+)-ATPase by the seleno-organic compound ebselen.
The effect of 2-phenyl-1,2-benzisoselenazol-3 (2H)-one (ebselen, CAS 60940-34-3), a seleno-organic compound, on the partial reaction steps of H+,K(+)-ATPase in hog leaky gastric vesicles was examined. Ebselen inhibited K(+)-dependent ATPase activity (IC50 = 0.06 mumol/l), phosphoenzyme formation (IC50 = 0.25 mumol/l), and K(+)-dependent p-nitrophenylphosphatase activity (IC50 = 0.09 mumol/l: dephosphorylation step of this enzyme). Furthermore, this compound prevented changes in the fluorescence intensity of flourescein isothiocyanate-labeled enzyme (E1-->E2K form, IC50 = 0.33 mumol/l). Pretreatment with 2 mmol/l of dithiothreitol (DTT) used as a sulfhydryl compound completely protected against these inhibitory effects. These findings indicate that ebselen-induced inactivation of gastric H+,K(+)-ATPase may result from prevention of the partial reaction steps, which include phosphorylation, dephosphorylation and conformational change (E1-->E2K form), through interference with sulfhydryl groups of the enzyme.
Tabuchi
Y
Y
Exploratory Research Laboratories III, Daiichi Pharmaceutical Co., Ltd., Tokyo, Japan.
Ogasawara
T
T
Furuhama
K
K
D009597:4-Nitrophenylphosphatase / Q000378:metabolism; D000818:Animals; D000897:Anti-Ulcer Agents / Q000494:pharmacology*; D001393:Azoles / Q000494:pharmacology*; D004229:Dithiothreitol / Q000494:pharmacology; D016650:Fluorescein-5-isothiocyanate; D005753:Gastric Mucosa / Q000187:drug effects / Q000201:enzymology*; D054833:Isoindoles; D016566:Organoselenium Compounds / Q000494:pharmacology*; D010766:Phosphorylation; D011487:Protein Conformation; D054328:Proton Pump Inhibitors; D013050:Spectrometry, Fluorescence; D013552:Swine
D000897:Anti-Ulcer Agents; D001393:Azoles; D054833:Isoindoles; D016566:Organoselenium Compounds; D054328:Proton Pump Inhibitors; C042986:ebselen; D009597:4-Nitrophenylphosphatase; D016650:Fluorescein-5-isothiocyanate; D004229:Dithiothreitol