title: The plasma membrane NADH oxidase of soybean has vitamin K(1) hydroquinone oxidase activity.
abstract: Isolated plasma membrane vesicles and the plasma membrane NADH oxidase partially purified from soybean plasma membrane vesicles exhibited a cyanide-insensitive vitamin K(1) hydroquinone oxidase activity with isolated plasma membrane vesicles. Reduced vitamin K(1) (phylloquinol) was oxidized at a rate of about 10 nmol/min/mg protein as determined by reduced vitamin K(1) reduction or oxygen consumption. The K(m) for reduced K(1) was 350 microM. With the partially purified enzyme, reduced vitamin K(1) was oxidized at a rate of about 600 nmol/min/mg protein and the K(m) was 400 microM. When assayed in the presence of 1 mM KCN, activities of both plasma membrane vesicles and of the purified protein were stimulated (0.1 microM) or inhibited (0.1 mM) by the synthetic auxin growth factor 2, 4-dichlorophenoxyacetic acid. The findings suggest the potential participation of the plasma membrane NADH oxidase as a terminal oxidase of plasma membrane electron transport from cytosolic NAD(P)H via reduced vitamin K(1) to acceptors (molecular oxygen or protein disulfides) at the cell surface.
authors.affiliation: Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: A
authors.initials: A
authors.lastname: Bridge
authors.forename: R
authors.initials: R
authors.lastname: Barr
authors.forename: D J
authors.initials: DJ
authors.lastname: Morré
mesh_terms: D002462:Cell Membrane / Q000201:enzymology*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D009097:Multienzyme Complexes / Q000302:isolation & purification / Q000378:metabolism*; D009247:NADH, NADPH Oxidoreductases / Q000302:isolation & purification / Q000378:metabolism*; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D012639:Seeds / Q000201:enzymology; D013025:Glycine max / Q000201:enzymology*; D013053:Spectrophotometry; D013379:Substrate Specificity; D010837:Vitamin K 1 / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism
chemical_list: D009097:Multienzyme Complexes; C028843:vitamin K1 hydroquinone; D010837:Vitamin K 1; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases