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Abstract
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/j-nitrophenyl phosphatase (K+-pNPPase) activity in a dose dependent manner with IC50 values of 2.3μM, AND 6.0μM 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 4.5μM. These results suggest that quercetin reduces the phosphorylated enzyme level by competition with ATP, and thereby inhibits the H+, K+-ATPase activity.