title: Evidence for a boat conformation at the transition state of GH76 α-1,6-mannanases--key enzymes in bacterial and fungal mannoprotein metabolism.
abstract: α-Mannosidases and α-mannanases have attracted attention for the insight they provide into nucleophilic substitution at the hindered anomeric center of α-mannosides, and the potential of mannosidase inhibitors as cellular probes and therapeutic agents. We report the conformational itinerary of the family GH76 α-mannanases studied through structural analysis of the Michaelis complex and synthesis and evaluation of novel aza/imino sugar inhibitors. A Michaelis complex in an (O) S2 conformation, coupled with distortion of an azasugar in an inhibitor complex to a high energy B2,5 conformation are rationalized through ab initio QM/MM metadynamics that show how the enzyme surface restricts the conformational landscape of the substrate, rendering the B2,5 conformation the most energetically stable on-enzyme. We conclude that GH76 enzymes perform catalysis using an itinerary that passes through (O) S2 and B2,5 (≠) conformations, information that should inspire the development of new antifungal agents.
authors.affiliation: Department of Chemistry, University of York, Heslington, York, YO10 5DD (UK).
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Thompson
authors.forename: Gaetano
authors.initials: G
authors.lastname: Speciale
authors.forename: Javier
authors.initials: J
authors.lastname: Iglesias-Fernández
authors.forename: Zalihe
authors.initials: Z
authors.lastname: Hakki
authors.forename: Tyson
authors.initials: T
authors.lastname: Belz
authors.forename: Alan
authors.initials: A
authors.lastname: Cartmell
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Spears
authors.forename: Emily
authors.initials: E
authors.lastname: Chandler
authors.forename: Max J
authors.initials: MJ
authors.lastname: Temple
authors.forename: Judith
authors.initials: J
authors.lastname: Stepper
authors.forename: Harry J
authors.initials: HJ
authors.lastname: Gilbert
authors.forename: Carme
authors.initials: C
authors.lastname: Rovira
authors.forename: Spencer J
authors.initials: SJ
authors.lastname: Williams
authors.forename: Gideon J
authors.initials: GJ
authors.lastname: Davies
mesh_terms: D001372:Aza Compounds / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D001407:Bacillus / Q000201:enzymology*; D001426:Bacterial Proteins / Q000378:metabolism*; D002176:Candida albicans / Q000201:enzymology*; D004791:Enzyme Inhibitors / Q000138:chemical synthesis* / Q000737:chemistry / Q000494:pharmacology; D005656:Fungal Proteins / Q000378:metabolism*; D050111:Imino Sugars / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D008361:Mannosidases / Q000037:antagonists & inhibitors* / Q000737:chemistry; D008958:Models, Molecular; D011487:Protein Conformation
chemical_list: D001372:Aza Compounds; D001426:Bacterial Proteins; D004791:Enzyme Inhibitors; D005656:Fungal Proteins; D050111:Imino Sugars; D008361:Mannosidases
keywords: carbohydrates; computational chemistry; conformational analysis; enzymatic mechanisms; glycosidase inhibitors