title: Binding Mode and Selectivity of Steroids towards Glucose-6-phosphate Dehydrogenase from the Pathogen Trypanosoma cruzi.
abstract: Glucose-6-phosphate dehydrogenase (G6PDH) plays a housekeeping role in cell metabolism by generating reducing power (NADPH) and fueling the production of nucleotide precursors (ribose-5-phosphate). Based on its indispensability for pathogenic parasites from the genus Trypanosoma, G6PDH is considered a drug target candidate. Several steroid-like scaffolds were previously reported to target the activity of G6PDH. Epiandrosterone (EA) is an uncompetitive inhibitor of trypanosomal G6PDH for which its binding site to the enzyme remains unknown. Molecular simulation studies with the structure of Trypanosoma cruzi G6PDH revealed that EA binds in a pocket close to the G6P binding-site and protrudes into the active site blocking the interaction between substrates and hence catalysis. Site directed mutagenesis revealed the important steroid-stabilizing effect of residues (L80, K83 and K84) located on helix α-1 of T. cruzi G6PDH. The higher affinity and potency of 16α-Br EA by T. cruzi G6PDH is explained by the formation of a halogen bond with the hydrogen from the terminal amide of the NADP+-nicotinamide. At variance with the human enzyme, the inclusion of a 21-hydroxypregnane-20-one moiety to a 3β-substituted steroid is detrimental for T. cruzi G6PDH inhibition. The species-specificity of certain steroid derivatives towards the parasite G6PDH and the corresponding biochemically validated binding models disclosed in this work may prove valuable for the development of selective inhibitors against the pathogen's enzyme.
authors.affiliation: Redox Biology of Trypanosomes, Institut Pasteur de Montevideo, Mataojo 2020, Montevideo 11400, Uruguay. cortiz@pasteur.edu.uy.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Ortiz
authors.affiliation: Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, Via Aldo Moro 2, Siena 53100, Italy. francesca.moraca@gmail.com.|Sbarro Institute for Cancer Research and Molecular Medicine, Center for Biotechnology, College of Science and Technology, Temple University, BioLife Science Building, Suite 333, 1900 N 12th Street, Philadelphia, PA 19122, USA. francesca.moraca@gmail.com.
authors.forename: Francesca
authors.initials: F
authors.lastname: Moraca
authors.affiliation: Redox Biology of Trypanosomes, Institut Pasteur de Montevideo, Mataojo 2020, Montevideo 11400, Uruguay. amedeiros@pasteur.edu.uy.|Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Av. Gral. Flores 2125, Montevideo 11800, Uruguay. amedeiros@pasteur.edu.uy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Medeiros
authors.affiliation: Dipartimento di Biotecnologie, Chimica e Farmacia, Università degli Studi di Siena, Via Aldo Moro 2, Siena 53100, Italy. botta.maurizio@gmail.com.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Botta
authors.affiliation: Drug Discovery Unit, Cancer Research, UK Manchester Institute, Wilmslow Road, Manchester M204BX, UK. Niall.Hamilton@cruk.manchester.ac.uk.
authors.forename: Niall
authors.initials: N
authors.lastname: Hamilton
authors.affiliation: Redox Biology of Trypanosomes, Institut Pasteur de Montevideo, Mataojo 2020, Montevideo 11400, Uruguay. mcomini@pasteur.edu.uy.
authors.forename: Marcelo A
authors.initials: MA
authors.lastname: Comini
mesh_terms: D000738:Androsterone / Q000378:metabolism / Q000493:pharmacokinetics*; D001665:Binding Sites; D014355:Chagas Disease / Q000188:drug therapy* / Q000469:parasitology; D005954:Glucosephosphate Dehydrogenase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D006801:Humans; D062105:Molecular Docking Simulation; D012267:Ribosemonophosphates / Q000378:metabolism; D013256:Steroids / Q000494:pharmacology; D014344:Trypanocidal Agents / Q000378:metabolism / Q000494:pharmacology; D014349:Trypanosoma cruzi / Q000187:drug effects / Q000472:pathogenicity
chemical_list: D012267:Ribosemonophosphates; D013256:Steroids; D014344:Trypanocidal Agents; C031626:ribose-5-phosphate; D000738:Androsterone; D005954:Glucosephosphate Dehydrogenase
keywords: Chagas disease; Leishmania; epiandrosterone; inhibition by steroids; pentose phosphate pathway; structure activity relationship