title: Pyrimidin-2(1H)-ones based inhibitors of Mycobacterium tuberculosis orotate phosphoribosyltransferase.
abstract: Tuberculosis (TB) is an ancient human chronic infectious disease caused mainly by Mycobacterium tuberculosis. The emergence of strains resistant to first and second line anti-TB drugs, associated with the increasing number of TB cases among HIV positive subjects, and the large number of individuals infected with latent bacilli have urged the development of new strategies to treat TB. Enzymes of nucleotide metabolism pathways provide promising molecular targets for the development of drugs, aiming at both active and latent TB. The orotate phosphoribosyltransferase (OPRT) enzyme catalyzes the synthesis of orotidine 5'-monophosphate from 5'-phospho-α-d-ribose 1'-diphosphate and orotic acid, in the de novo pyrimidine synthesis pathway. Based on the kinetic mechanism and molecular properties, here we describe the design, selection and synthesis of substrate analogs with inhibitory activity of M. tuberculosis OPRT (MtOPRT) enzyme. Steady-state kinetic measurements were employed to determine the mode of inhibition of commercially available and chemically derived compounds. The 6-Hydroxy-2-oxo-1,2-dihydropyridine-4-carboxylic acid (6) chemical compound and its derivative, 3-Benzylidene-2,6-dioxo-1,2,3,6-tetrahydropyridine-4-carboxylic acid (13), showed enzyme inhibition constants in the submicromolar range. Isothermal titration calorimetry data indicated that binding of both compounds to MtOPRT have negative enthalpy and favorable Gibbs free energy probably due to their high complementarity to the enzyme's binding pocket. Improvement of compound 13 hydrophobic character by addition of an aromatic ring substituent resulted in entropic optimization, reflected on a thermodynamic discrimination profile characteristic of high affinity ligands. These inhibitors represent lead compounds for further development of MtOPRT inhibitors with increased potency, which may be tested as anti-TB agents.
authors.affiliation: Instituto Nacional de Ciência e Tecnologia em Tuberculose, Pontifícia Universidade Católica do Rio Grande do Sul, Avenida Ipiranga 6900, Prédio 92A - TECNOPUC, 90619-900 Porto Alegre, Rio Grande do Sul, Brazil. ardalabreda@gmail.com
authors.forename: Ardala
authors.initials: A
authors.lastname: Breda
authors.forename: Pablo
authors.initials: P
authors.lastname: Machado
authors.forename: Leonardo Astolfi
authors.initials: LA
authors.lastname: Rosado
authors.forename: André Arigony
authors.initials: AA
authors.lastname: Souto
authors.forename: Diógenes Santiago
authors.initials: DS
authors.lastname: Santos
authors.forename: Luiz Augusto
authors.initials: LA
authors.lastname: Basso
mesh_terms: D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D009169:Mycobacterium tuberculosis / Q000187:drug effects / Q000201:enzymology*; D009962:Orotate Phosphoribosyltransferase / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011744:Pyrimidinones / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D011744:Pyrimidinones; D009962:Orotate Phosphoribosyltransferase