title: Stimulation of the chlorinating activity of human myeloperoxidase by thyroid hormones and analogues.
abstract: Thyroxine and triiodothyronine concentrations of 50 nM or lower can stimulate the chlorinating activity of the myeloperoxidase-H2O2-Cl- antimicrobial system in vitro. The initial rates of the chlorinating reaction with monochlorodimedone were similar for both thyroid hormones. Maximum stimulation occurred around pH 6 and a linear relationship exists between stimulation and thyroxine concentrations up to at least 1 microM. Of the various thyroxine analogues tested, stimulation was in the order: T4 (or T3) greater than triiodothyropropionic acid greater than 3,5-T2. Diiodotyrosine did not have any significant stimulatory effect. The oxidised product of the phenolic ring of T4, presumably a hydroxyquinone, may act as an additional electron carrier and thereby facilitates redox reactions.
authors.affiliation: Department of Pharmacology, University of Stellenbosch, Medical School, Tygerberg, South Africa.
authors.forename: J M
authors.initials: JM
authors.lastname: Van Zyl
authors.forename: K
authors.initials: K
authors.lastname: Basson
authors.forename: B J
authors.initials: BJ
authors.lastname: Van der Walt
mesh_terms: D002712:Chlorides / Q000378:metabolism; D002713:Chlorine / Q000378:metabolism*; D003512:Cyclohexanones / Q000378:metabolism; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D009504:Neutrophils / Q000201:enzymology; D009195:Peroxidase / Q000378:metabolism*; D010544:Peroxidases / Q000378:metabolism; D013268:Stimulation, Chemical; D013963:Thyroid Hormones / Q000494:pharmacology*; D013974:Thyroxine / Q000494:pharmacology; D014284:Triiodothyronine / Q000494:pharmacology
chemical_list: D002712:Chlorides; D003512:Cyclohexanones; D013963:Thyroid Hormones; D014284:Triiodothyronine; D002713:Chlorine; C006991:chlorodimedone; D006861:Hydrogen Peroxide; D010544:Peroxidases; D009195:Peroxidase; D013974:Thyroxine