title: Imidazole antibiotics inhibit the nitric oxide dioxygenase function of microbial flavohemoglobin.
abstract: Flavohemoglobins metabolize nitric oxide (NO) to nitrate and protect bacteria and fungi from NO-mediated damage, growth inhibition, and killing by NO-releasing immune cells. Antimicrobial imidazoles were tested for their ability to coordinate flavohemoglobin and inhibit its NO dioxygenase (NOD) function. Miconazole, econazole, clotrimazole, and ketoconazole inhibited the NOD activity of Escherichia coli flavohemoglobin with apparent K(i) values of 80, 550, 1,300, and 5,000 nM, respectively. Saccharomyces cerevisiae, Candida albicans, and Alcaligenes eutrophus enzymes exhibited similar sensitivities to imidazoles. Imidazoles coordinated the heme iron atom, impaired ferric heme reduction, produced uncompetitive inhibition with respect to O(2) and NO, and inhibited NO metabolism by yeasts and bacteria. Nevertheless, these imidazoles were not sufficiently selective to fully mimic the NO-dependent growth stasis seen with NOD-deficient mutants. The results demonstrate a mechanism for NOD inhibition by imidazoles and suggest a target for imidazole engineering.
authors.affiliation: Division of Critical Care Medicine, Children's Hospital Medical Center, Cincinnati, Ohio 45229, USA.
authors.forename: Ryan A
authors.initials: RA
authors.lastname: Helmick
authors.forename: Arin E
authors.initials: AE
authors.lastname: Fletcher
authors.forename: Anne M
authors.initials: AM
authors.lastname: Gardner
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Gessner
authors.forename: Angela N
authors.initials: AN
authors.lastname: Hvitved
authors.forename: Michael C
authors.initials: MC
authors.lastname: Gustin
authors.forename: Paul R
authors.initials: PR
authors.lastname: Gardner
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002176:Candida albicans / Q000187:drug effects / Q000201:enzymology; D004093:Dihydropteridine Reductase / Q000037:antagonists & inhibitors* / Q000235:genetics; D004791:Enzyme Inhibitors; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D005182:Flavin-Adenine Dinucleotide / Q000378:metabolism; D006418:Heme / Q000378:metabolism; D006420:Hemeproteins / Q000037:antagonists & inhibitors* / Q000235:genetics; D007093:Imidazoles / Q000494:pharmacology*; D007700:Kinetics; D009243:NAD / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000037:antagonists & inhibitors* / Q000235:genetics; D009569:Nitric Oxide / Q000378:metabolism; D010084:Oxidation-Reduction; D010105:Oxygenases / Q000037:antagonists & inhibitors* / Q000235:genetics; D010957:Plasmids
chemical_list: D000900:Anti-Bacterial Agents; D004791:Enzyme Inhibitors; D029968:Escherichia coli Proteins; D006420:Hemeproteins; D007093:Imidazoles; D009243:NAD; D005182:Flavin-Adenine Dinucleotide; D009569:Nitric Oxide; D006418:Heme; D010105:Oxygenases; C114415:nitric oxide dioxygenase; D004093:Dihydropteridine Reductase; C076538:hmp protein, E coli; D009247:NADH, NADPH Oxidoreductases