title: The nitric oxide transduction pathway in Trypanosoma cruzi.
abstract: A nitric oxide synthase was partially purified from soluble extracts of Trypanosoma cruzi epimastigote forms. The conversion of L-arginine to citrulline by this enzyme activity required NADPH and was blocked by EGTA. The reaction was activated by Ca2+, calmodulin, tetrahydrobiopterin, and FAD, and inhibited by N omega-methyl-L-arginine. L-Glutamate and N-methyl-D-aspartate stimulated in vivo conversion of L-arginine to citrulline by epimastigote cells. These stimulations could be blocked by EGTA, MK-801, and ketamine and enhanced by glycine. A sodium nitroprusside-activated guanylyl cyclase activity was detected in cell-free, soluble preparations of T. cruzi epimastigotes. L-Glutamate, N-methyl-D-aspartate, and sodium nitroprusside increased epimastigote cyclic GMP levels. MK-801 bound specifically to T. cruzi epimastigote cells. This binding was competed by ketamine and enhanced by glycine or L-serine. Evidence thus indicates that in T. cruzi epimastigotes, L-glutamate controls cyclic GMP levels through a pathway mediated by nitric oxide.
authors.affiliation: Instituto de Investigaciones en Ingeniería Genética y Biología Molecular, CONICET, Universidad de Buenos Aires.
authors.forename: C
authors.initials: C
authors.lastname: Paveto
authors.forename: C
authors.initials: C
authors.lastname: Pereira
authors.forename: J
authors.initials: J
authors.lastname: Espinosa
authors.forename: A E
authors.initials: AE
authors.lastname: Montagna
authors.forename: M
authors.initials: M
authors.lastname: Farber
authors.forename: M
authors.initials: M
authors.lastname: Esteva
authors.forename: M M
authors.initials: MM
authors.lastname: Flawiá
authors.forename: H N
authors.initials: HN
authors.lastname: Torres
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D000818:Animals; D001120:Arginine / Q000378:metabolism; D002956:Citrulline / Q000378:metabolism; D006152:Cyclic GMP / Q000032:analysis; D016291:Dizocilpine Maleate / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism; D009569:Nitric Oxide / Q000502:physiology*; D019001:Nitric Oxide Synthase; D016194:Receptors, N-Methyl-D-Aspartate / Q000502:physiology; D014349:Trypanosoma cruzi / Q000378:metabolism*
chemical_list: D016194:Receptors, N-Methyl-D-Aspartate; D002956:Citrulline; D009569:Nitric Oxide; D016291:Dizocilpine Maleate; D001120:Arginine; D019001:Nitric Oxide Synthase; D000594:Amino Acid Oxidoreductases; D006162:Guanylate Cyclase; D006152:Cyclic GMP