title: Mechanism of melatonin-induced oscillations in the peroxidase-oxidase reaction.
abstract: Melatonin induces oscillations in the peroxidase-oxidase (PO) reaction catalyzed by horseradish peroxidase. We present here studies of the effect of pH, enzyme concentration, and concentration of melatonin on the oscillation frequency. We also present a mechanistic model to explain the experimentally observed changes in oscillation frequency. Using the data obtained here we are able to predict that oscillations will also occur in the PO reaction catalyzed by myeloperoxidase. Myeloperoxidase is an important protein in activated neutrophils and we provide evidence that the oscillations of NAD(P)H, superoxide and hydrogen peroxide in these cells may involve this enzyme. Thus, our experimental system can be considered a model system for the nonrespiratory oxygen metabolism in activated neutrophils and other similar cells participating in the defence against invading pathogens.
authors.affiliation: Celcom, Department of Biochemistry and Molecular Biology, Syddansk Universitet, Campusvej 55, DK-5230 Odense M, Denmark. lfo@bmb.sdu.dk
authors.forename: Lars Folke
authors.initials: LF
authors.lastname: Olsen
authors.forename: Anita
authors.initials: A
authors.lastname: Lunding
authors.forename: Ursula
authors.initials: U
authors.lastname: Kummer
mesh_terms: D004305:Dose-Response Relationship, Drug; D006735:Horseradish Peroxidase / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D008550:Melatonin / Q000494:pharmacology*; D008956:Models, Chemical; D009249:NADP / Q000378:metabolism; D009504:Neutrophils / Q000201:enzymology; D016877:Oxidants / Q000494:pharmacology; D010088:Oxidoreductases / Q000378:metabolism*; D010101:Oxygen Consumption; D009195:Peroxidase / Q000494:pharmacology; D010544:Peroxidases / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism; D013997:Time Factors
chemical_list: D016877:Oxidants; D013481:Superoxides; D009249:NADP; D006861:Hydrogen Peroxide; D010088:Oxidoreductases; D006735:Horseradish Peroxidase; D010544:Peroxidases; D009195:Peroxidase; D008550:Melatonin