title: Structural Basis for the Inhibition of Helicobacter pylori α-Carbonic Anhydrase by Sulfonamides.
abstract: Periplasmic α-carbonic anhydrase of Helicobacter pylori (HpαCA), an oncogenic bacterium in the human stomach, is essential for its acclimation to low pH. It catalyses the conversion of carbon dioxide to bicarbonate using Zn(II) as the cofactor. In H. pylori, Neisseria spp., Brucella suis and Streptococcus pneumoniae this enzyme is the target for sulfonamide antibacterial agents. We present structural analysis correlated with inhibition data, on the complexes of HpαCA with two pharmacological inhibitors of human carbonic anhydrases, acetazolamide and methazolamide. This analysis reveals that two sulfonamide oxygen atoms of the inhibitors are positioned proximal to the putative location of the oxygens of the CO2 substrate in the Michaelis complex, whilst the zinc-coordinating sulfonamide nitrogen occupies the position of the catalytic water molecule. The structures are consistent with acetazolamide acting as site-directed, nanomolar inhibitors of the enzyme by mimicking its reaction transition state. Additionally, inhibitor binding provides insights into the channel for substrate entry and product exit. This analysis has implications for the structure-based design of inhibitors of bacterial carbonic anhydrases.
authors.forename: Joyanta K
authors.initials: JK
authors.lastname: Modak
authors.affiliation: Department of Microbiology, Faculty of Biomedical and Psychological Sciences, Monash University, Clayton, Victoria, Australia.
authors.forename: Joyanta K
authors.initials: JK
authors.lastname: Modakh
authors.affiliation: Department of Microbiology, Faculty of Biomedical and Psychological Sciences, Monash University, Clayton, Victoria, Australia.
authors.forename: Yu C
authors.initials: YC
authors.lastname: Liu
authors.affiliation: Department of Microbiology, Faculty of Biomedical and Psychological Sciences, Monash University, Clayton, Victoria, Australia.
authors.forename: Mayra A
authors.initials: MA
authors.lastname: Machuca
authors.affiliation: Laboratorio di Chimica Bioinorganica, Polo Scientifico, Università degli Studi di Firenze, Via della Lastruccia 3, Sesto Fiorentino (Florence) Italy; Neurofarba Department, Sezione di Scienze Farmaceutiche, Università degli Studi di Firenze, Via U. Schiff 6, Sesto Fiorentino (Firenze), Italy.
authors.forename: Claudiu T
authors.initials: CT
authors.lastname: Supuran
authors.affiliation: Department of Microbiology, Faculty of Biomedical and Psychological Sciences, Monash University, Clayton, Victoria, Australia; Department of Biochemistry and Molecular Biology, Faculty of Biomedical and Psychological Sciences, Monash University, Clayton, Victoria, Australia.
authors.forename: Anna
authors.initials: A
authors.lastname: Roujeinikova
mesh_terms: D000086:Acetazolamide / Q000494:pharmacology; D000595:Amino Acid Sequence; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology*; D002256:Carbonic Anhydrases / Q000378:metabolism*; D016481:Helicobacter Infections / Q000188:drug therapy / Q000382:microbiology; D016480:Helicobacter pylori / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D008704:Methazolamide / Q000494:pharmacology; D008969:Molecular Sequence Data; D019897:Periplasm / Q000187:drug effects / Q000378:metabolism; D016415:Sequence Alignment; D013449:Sulfonamides / Q000494:pharmacology*
chemical_list: D000900:Anti-Bacterial Agents; D002257:Carbonic Anhydrase Inhibitors; D013449:Sulfonamides; D002256:Carbonic Anhydrases; D000086:Acetazolamide; D008704:Methazolamide