title: Methylene blue competes with paraquat for reduction by flavo-enzymes resulting in decreased superoxide production in the presence of heme proteins.
abstract: Methylene blue competes 100 to 600 times more effectively than paraquat for reduction by three different flavo-containing enzymes; xanthine oxidase, NADH cytochrome c reductase, and NADPH cytochrome c reductase. Paraquat and methylene blue both interact with deflavo xanthine oxidase, indicating that neither electron acceptor reacted at the FAD site of the enzyme where molecular oxygen is reduced to superoxide. As the paraquat radical also directly reduced acetylated cytochrome c the hemeprotein could not be utilized for measuring superoxide production in the presence of the herbicide. In the presence of cytochrome c the methylene blue caused a sharp decrease in both paraquat-induced superoxide and hydroxyl radical production.
authors.affiliation: Department of Pathology, University of California, San Diego 92103.
authors.forename: M J
authors.initials: MJ
authors.lastname: Kelner
authors.forename: R
authors.initials: R
authors.lastname: Bagnell
authors.forename: B
authors.initials: B
authors.lastname: Hale
authors.forename: N M
authors.initials: NM
authors.lastname: Alexander
mesh_terms: D003579:Cytochrome Reductases / Q000378:metabolism*; D005609:Free Radicals; D006418:Heme / Q000378:metabolism*; D008751:Methylene Blue / Q000378:metabolism*; D009245:NADH Dehydrogenase / Q000378:metabolism*; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism*; D010084:Oxidation-Reduction; D010269:Paraquat / Q000378:metabolism*; D013379:Substrate Specificity; D013481:Superoxides / Q000096:biosynthesis*; D014969:Xanthine Oxidase / Q000378:metabolism*
chemical_list: D005609:Free Radicals; D013481:Superoxides; D006418:Heme; D014969:Xanthine Oxidase; D003579:Cytochrome Reductases; D009251:NADPH-Ferrihemoprotein Reductase; D009245:NADH Dehydrogenase; D010269:Paraquat; D008751:Methylene Blue