title: Oxygen activation at the plasma membrane: relation between superoxide and hydroxyl radical production by isolated membranes.
abstract: Production of reactive oxygen species (hydroxyl radicals, superoxide radicals and hydrogen peroxide) was studied using EPR spin-trapping techniques and specific dyes in isolated plasma membranes from the growing and the non-growing zones of hypocotyls and roots of etiolated soybean seedlings as well as coleoptiles and roots of etiolated maize seedlings. NAD(P)H mediated the production of superoxide in all plasma membrane samples. Hydroxyl radicals were only produced by the membranes of the hypocotyl growing zone when a Fenton catalyst (FeEDTA) was present. By contrast, in membranes from other parts of the seedlings a low rate of spontaneous hydroxyl radical formation was observed due to the presence of small amounts of tightly bound peroxidase. It is concluded that apoplastic hydroxyl radical generation depends fully, or for the most part, on peroxidase localized in the cell wall. In soybean plasma membranes from the growing zone of the hypocotyl pharmacological tests showed that the superoxide production could potentially be attributed to the action of at least two enzymes, an NADPH oxidase and, in the presence of menadione, a quinone reductase.
authors.affiliation: Commissariat à l'Energie Atomique (CEA Saclay), iBiTec-S, CNRS URA 2096, Service de Bioénergétique Biologie Structurale et Mécanisme, Bât. 532, 91191 Gif-sur-Yvette, France.
authors.forename: Eiri
authors.initials: E
authors.lastname: Heyno
authors.forename: Véronique
authors.initials: V
authors.lastname: Mary
authors.forename: Peter
authors.initials: P
authors.lastname: Schopfer
authors.forename: Anja
authors.initials: A
authors.lastname: Krieger-Liszkay
mesh_terms: D002462:Cell Membrane / Q000201:enzymology / Q000378:metabolism*; D018548:Cotyledon / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D017665:Hydroxyl Radical / Q000378:metabolism; D018546:Hypocotyl / Q000378:metabolism; D019255:NADPH Oxidases / Q000378:metabolism; D010100:Oxygen / Q000378:metabolism*; D009195:Peroxidase / Q000378:metabolism; D018517:Plant Roots / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D013025:Glycine max / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D003313:Zea mays / Q000378:metabolism*
chemical_list: D017382:Reactive Oxygen Species; D013481:Superoxides; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; D009195:Peroxidase; D019255:NADPH Oxidases; D010100:Oxygen