title: Evaluation of the non-catalytic binding function of Ts26GST a glutathione transferase isoform of Taenia solium.
abstract: Taenia solium glutathione transferase isoform of 26.5 kDa (Ts26GST) was observed to bind non-catalytically to porphyrins, trans-trans-dienals, bile acids and fatty acids, as assessed by inhibition kinetics, fluorescence spectroscopy and competitive fluorescence assays with 8-anilino-1-naphthalene sulfonate (ANS). The quenching of Ts26GST intrinsic fluorescence allowed for the determination of the dissociation constants (KD) for all ligands. Obtained data indicate that Ts26GST binds to all ligands but with different affinity. Porphyrins and lipid peroxide products inhibited Ts26GST catalytic activity up to 100% in contrast with only 20-30% inhibition observed for bile acids and two saturated fatty acids. Non-competitive type inhibition was observed for all enzyme inhibitor ligands except for trans-trans-2,4-decadienal, which exhibited uncompetitive type inhibition. The dissociation constant value KD = 0.7 μM for the hematin ligand, determined by competitive fluorescence assays with ANS, was in good agreement with its inhibition kinetic value Ki = 0.3 μM and its intrinsic fluorescence quenching KD = 0.7 μM. The remaining ligands did not displace ANS from the enzyme suggesting the existence of different binding sites. In addition to the catalytic activity of Ts26GST the results obtained suggest that the enzyme exhibits a ligandin function with broad specificity towards nonsubstrate ligands.
authors.affiliation: Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, UNAM, México, D.F. 04510, Mexico. Electronic address: apc@servidor.unam.mx.
authors.forename: A
authors.initials: A
authors.lastname: Plancarte
authors.affiliation: Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, UNAM, México, D.F. 04510, Mexico.
authors.forename: J R
authors.initials: JR
authors.lastname: Romero
authors.affiliation: Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, UNAM, México, D.F. 04510, Mexico.
authors.forename: G
authors.initials: G
authors.lastname: Nava
authors.affiliation: Laboratorio de Bioquímica-Genética y División de Investigación, Instituto Nacional de Pediatría, D.F., Mexico.
authors.forename: H
authors.initials: H
authors.lastname: Reyes
authors.affiliation: Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad Nacional Autónoma de México, UNAM, México, D.F. 04510, Mexico.
authors.forename: M
authors.initials: M
authors.lastname: Hernández
mesh_terms: D000447:Aldehydes / Q000378:metabolism; D000817:Anilino Naphthalenesulfonates / Q000378:metabolism; D000818:Animals; D001647:Bile Acids and Salts / Q000378:metabolism; D001667:Binding, Competitive; D003551:Cysticercosis / Q000469:parasitology / Q000662:veterinary; D005227:Fatty Acids / Q000378:metabolism; D005982:Glutathione Transferase / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D020128:Inhibitory Concentration 50; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism; D007700:Kinetics; D008024:Ligands; D011166:Porphyrins / Q000378:metabolism; D013050:Spectrometry, Fluorescence; D013552:Swine; D013553:Swine Diseases / Q000469:parasitology; D041201:Taenia solium / Q000201:enzymology*
chemical_list: C515594:8-anilino-1-naphthalenesulfonic acid; D000447:Aldehydes; D000817:Anilino Naphthalenesulfonates; D001647:Bile Acids and Salts; D005227:Fatty Acids; D007527:Isoenzymes; D008024:Ligands; D011166:Porphyrins; D005982:Glutathione Transferase
keywords: Fluorescence; Glutathione S-transferase; Helminths; Kinetic; Ligandin; Taenia solium