title: Interaction of beta-eudesmol with Na+,K(+)-ATPase: inhibition of K(+)-pNPPase activity.
abstract: The effect of beta-eudesmol, one of the major components in So-jutsu (Atractylodis Lanceae Rhizoma), on K(+)-dependent p-nitrophenyl phosphatase (K(+)-pNPPase) activity was studied. It inhibited K(+)-pNPPase activity with an I50 value of 4.1 x 10(-4) M. The inhibition rate decreased as the K+ concentration was increased, whereas greater inhibition was observed with high concentrations of either Na+ or ATP. The Ki values for Na+ in the presence of 0, 0.1 and 1 mM ATP were 140, 260 and 310 mM, respectively, but with the addition of beta-eudesmol, these values decreased to 90 mM regardless of the ATP concentration. This study on K(+)-pNPPase activity supports the conclusion obtained from the study on Na+,K(+)-ATPase activity (Satoh K et al., Biochem Pharmacol 44: 373-378, 1992) that is, beta-eudesmol interacts with enzyme in the Na.E1 form and inhibits the reaction step Na.E1----Na.E1-P. Furthermore, in the study of the effects of K+ and beta-eudesmol on K(+)-pNPPase activity, it was confirmed that beta-eudesmol prevents the conformational change of Na.E1----K.E2.
authors.affiliation: Department of Toxicology, Tokyo Metropolitan Research Laboratory of Public Health, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Satoh
authors.forename: F
authors.initials: F
authors.lastname: Nagai
authors.forename: I
authors.initials: I
authors.lastname: Kano
mesh_terms: D009597:4-Nitrophenylphosphatase / Q000037:antagonists & inhibitors*; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D004305:Dose-Response Relationship, Drug; D006736:Horses; D007668:Kidney / Q000201:enzymology; D007700:Kinetics; D045787:Sesquiterpenes, Eudesmane; D012965:Sodium Chloride / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013729:Terpenes / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D045787:Sesquiterpenes, Eudesmane; D013729:Terpenes; D012965:Sodium Chloride; C051082:beta-eudesmol; D000255:Adenosine Triphosphate; D009597:4-Nitrophenylphosphatase; D000254:Sodium-Potassium-Exchanging ATPase