Inhibition of gastric H+, K(+)-ATPase by quercetin.
The effects of the naturally occurring flavonoid, quercetin, on gastric H+, K(+)-ATPase were investigated. Quercetin inhibited hog gastric H+, K(+)-ATPase and K(+)-stimulated p-nitrophenyl phosphatase (K(+)-pNPPase) activity in a dose dependent manner with IC50 values of 2.3 microM, and 6.0 microM respectively. The inhibition of H+, K(+)-ATPase by quercetin is competitive with ATP and is noncompetitive with K+. The steady-state phosphorylation level of the enzyme was also dose-dependently reduced by quercetin with an IC50 value of 4.5 microM. These results suggest that quercetin reduces the phosphorylated enzyme level by competition with ATP, and thereby inhibits the H+, K(+)-ATPase activity.
Murakami
S
S
Research Center, Taisho Pharmaceutical Co. Ltd., Saitama, Japan.
Muramatsu
M
M
Otomo
S
S
D009597:4-Nitrophenylphosphatase / Q000037:antagonists & inhibitors*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001667:Binding, Competitive; D002462:Cell Membrane / Q000201:enzymology; D007700:Kinetics; D009130:Muscle, Smooth / Q000201:enzymology; D011188:Potassium / Q000494:pharmacology; D054328:Proton Pump Inhibitors; D011794:Quercetin / Q000494:pharmacology*; D013270:Stomach / Q000201:enzymology*; D013552:Swine
D054328:Proton Pump Inhibitors; D000255:Adenosine Triphosphate; D011794:Quercetin; D009597:4-Nitrophenylphosphatase; D011188:Potassium