title: The proton pump inhibitor, E3810, binds to the N-terminal half of the alpha-subunit of gastric H+,K(+)-ATPase.
abstract: E3810 (2-([4-(3-methoxypropoxy)-3-methylpyridine-2-yl]methylsulphinyl )- 1H-benzimidazole sodium salt), an inhibitor of gastric proton pump (gastric H+,K(+)-ATPase), is activated in a luminal acidic environment of gastric glands and binds to a Cys residue of H+,K(+)-ATPase on its luminal side. It was found that bound E3810 is transformed into a strongly fluorescent compound by UV-light irradiation (excitation wavelength = 335 nm, emission wavelength = 470 nm). The location of Cys residue bound with E3810 in the alpha-subunit of hog gastric H+,K(+)-ATPase was estimated from the fluorescence labelling and limited tryptic digestion of the enzyme. Tryptic digestion in the presence of Mg-ATP produces N-terminal 67 kDa subfragment which contains the phosphorylation and fluorescein 5'-isothiocyanate binding sites and C-terminal 35 kDa subfragment. Trypsin digestion in the presence of KCl produces N-terminal 42 kDa and C-terminal 56 kDa subfragments. E3810 was found to bind to both N-terminal but not to any of two C-terminal subfragments. Taking the amino acid sequence and topology of this ATPase as well as the fact that the ratio of specific binding sites per alpha-subunit is one into consideration, the possibility that E3810 specifically binds to Cys322 residue of hog gastric H+,K(+)-ATPase is discussed.
authors.affiliation: Faculty of Pharmaceutical Sciences, Toyama Medical and Pharmaceutical University, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Morii
authors.forename: K
authors.initials: K
authors.lastname: Hamatani
authors.forename: N
authors.initials: N
authors.lastname: Takeguchi
mesh_terms: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D000818:Animals; D001562:Benzimidazoles / Q000378:metabolism*; D005456:Fluorescent Dyes; D017506:H(+)-K(+)-Exchanging ATPase / Q000737:chemistry / Q000378:metabolism*; D009853:Omeprazole / Q000031:analogs & derivatives; D054328:Proton Pump Inhibitors; D064750:Rabeprazole; D013270:Stomach / Q000201:enzymology*; D013552:Swine; D014357:Trypsin / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: D053799:2-Pyridinylmethylsulfinylbenzimidazoles; D001562:Benzimidazoles; D005456:Fluorescent Dyes; D054328:Proton Pump Inhibitors; D064750:Rabeprazole; D014357:Trypsin; D017506:H(+)-K(+)-Exchanging ATPase; D009853:Omeprazole