title: NADH oxidase activity of soybean plasma membranes inhibited by submicromolar concentrations of ATP.
abstract: The activity of an auxin-stimulated NADH oxidase activity from soybean hypocotyls was inhibited by submicromolar concentrations of ATP. Auxins are plant growth regulators that increase the rate of cell enlargement in plant stems. A synthetic auxin, 2,4-dichlorophenoxyacetic acid (2,4-D), was used. The inhibition was half maximal at 1 nM ATP and was not observed with other nucleotides and nucleosides. The inhibition was the result of an increase in the Km for NADH from about 60 microM to > 100 microM and was noncompetitive. The decrease in Km due to ATP was enhanced by the addition of 1 microM 2,4-D. The Vmax of the plasma membrane NADH oxidase was approximately doubled (1.5-2.8-fold) by ATP and by 1 microM 2,4-D. No further increase in the Vmax was observed by the combination of 1 nM to 0.1 mM ATP in the presence of 1 microM 2,4-D. The results demonstrate a response of the NADH oxidase activity of isolated vesicles of soybean plasma membranes to ATP distinct from that observed previously with other nucleotide di- and triphosphates. The results are suggestive either of control of the cell surface NADH oxidase by phosphorylation or a direct response to ATP binding at nanomolar concentrations of ATP.
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907-1333, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Morré
mesh_terms: D015084:2,4-Dichlorophenoxyacetic Acid / Q000494:pharmacology; D000244:Adenosine Diphosphate / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D002462:Cell Membrane / Q000201:enzymology*; D000242:Cyclic AMP / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005978:Glutathione / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007700:Kinetics; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009243:NAD / Q000378:metabolism / Q000494:pharmacology; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010084:Oxidation-Reduction; D012639:Seeds / Q000201:enzymology; D013025:Glycine max / Q000201:enzymology*
chemical_list: D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D009243:NAD; D015084:2,4-Dichlorophenoxyacetic Acid; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D006861:Hydrogen Peroxide; D000242:Cyclic AMP; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D005978:Glutathione