title: Trypanosoma cruzi dihydrolipoamide dehydrogenase is inactivated by myeloperoxidase-generated "reactive species".
abstract: Dihydrolipoamide dehydrogenase (LADH) from Trypanosoma cruzi was inactivated by treatment with myeloperoxidase (MPO)-dependent systems. With MPO/H2O2/NaCl, LADH lipoamide reductase and diaphorase activities significantly decreased as a function of incubation time. Iodide, bromide, thiocyanide and chloride effectively supplemented the MPO/H2O2 system, KI and NaCl being the most and the least effective supplements, respectively. LADH inactivation by MPO/H2O2/NaCl and by NaOCl was similarly prevented by thiol compounds such as GSH, L-cysteine, N-acetylcysteine, penicillamine and N-(2-mercaptopropionyl-glycine) in agreement with the role of HOCI in LADH inactivation by MPO/H2O2/NaCl. LADH was also inactivated by MPO/NADH/halide, MPO/H2O2/NaNO2 and MPO/NADH/NaNO2 systems. Catalase prevented the action of the NADH-dependent systems, thus supporting H2O2 production by NADH-supplemented LADH. MPO inhibitors (4-aminobenzoic acid hydrazide, and isoniazid), GSH, L-cysteine, L-methionine and L-tryptophan prevented LADH inactivation by MPO/H2O2/NaNO2. Other MPO systems inactivating LADH were (a) MPO/H2O2/chlorpromazine; (b) MPO/H2O2/monophenolic systems, including L-tyrosine, serotonin and acetaminophen and (c) MPO/H2O2/di- and polyphenolic systems, including norepinephrine, catechol, nordihydroguaiaretic acid, caffeic acid, quercetin and catechin. Comparison of the above effects and those previously reported with pig myocardial LADH indicates that both enzymes were similarly affected by the MPO-dependent systems, allowance being made for T. cruzi LADH diaphorase inactivation and the greater sensitivity of its LADH lipoamide reductase activity towards the MPO/H2O2/NaCl system and NaOCl.
authors.affiliation: Bioenergetics Research Centre, School of Medicine, University of Buenos Aires, Argentina.
authors.forename: J
authors.initials: J
authors.lastname: Gutierrez-Correa
authors.forename: R L
authors.initials: RL
authors.lastname: Krauth-Siegel
authors.forename: A O
authors.initials: AO
authors.lastname: Stoppani
mesh_terms: D000818:Animals; D008058:Dihydrolipoamide Dehydrogenase / Q000037:antagonists & inhibitors*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D066298:In Vitro Techniques; D009195:Peroxidase / Q000378:metabolism* / Q000494:pharmacology; D019800:Phenol / Q000378:metabolism / Q000494:pharmacology; D010640:Phenothiazines / Q000378:metabolism / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D012492:Salts / Q000378:metabolism / Q000494:pharmacology; D012977:Sodium Nitrite / Q000378:metabolism / Q000494:pharmacology; D014349:Trypanosoma cruzi / Q000201:enzymology*
chemical_list: D004791:Enzyme Inhibitors; D010640:Phenothiazines; D017382:Reactive Oxygen Species; D012492:Salts; D019800:Phenol; D006861:Hydrogen Peroxide; D009195:Peroxidase; D008058:Dihydrolipoamide Dehydrogenase; D012977:Sodium Nitrite