title: Tuning mechanism-based inactivators of neuraminidases: mechanistic and structural insights.
abstract: 3-Fluorosialosyl fluorides are inhibitors of sialidases that function by the formation of a long-lived covalent active-site adduct and have potential as therapeutics if made specific for the pathogen sialidase. Surprisingly, human Neu2 and the Trypanosoma cruzi trans-sialidase are inactivated more rapidly by the reagent with an equatorial fluorine at C3 than by its axial epimer, with reactivation following the same pattern. To explore a possible stereoelectronic basis for this, rate constants for spontaneous hydrolysis of the full series of four 3-fluorosialosyl fluorides were measured, and ground-state energies for each computed. The alpha (equatorial) anomeric fluorides hydrolyze more rapidly than their beta anomers, consistent with their higher ground-state energies. However ground-state energies do not explain the relative spontaneous reactivities of the 3-fluoro-epimers. The three-dimensional structures of the two 3-fluoro-sialosyl enzyme intermediates of human Neu2 were solved, revealing key stabilizing interactions between Arg21 and the equatorial, but not the axial, fluorine. Because of changes in geometry these interactions will increase at the transition state, likely explaining the difference in reaction rates.
authors.affiliation: Department of Chemistry, University of British Columbia, Vancouver, B. C., V6T 1Z1 (Canada).
authors.forename: Sabrina
authors.initials: S
authors.lastname: Buchini
authors.forename: François-Xavier
authors.initials: FX
authors.lastname: Gallat
authors.forename: Ian R
authors.initials: IR
authors.lastname: Greig
authors.forename: Jin-Hyo
authors.initials: JH
authors.lastname: Kim
authors.forename: Soichi
authors.initials: S
authors.lastname: Wakatsuki
authors.forename: Leonard M G
authors.initials: LM
authors.lastname: Chavas
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Withers
mesh_terms: D006801:Humans; D006868:Hydrolysis; D008958:Models, Molecular; D009439:Neuraminidase / Q000037:antagonists & inhibitors* / Q000737:chemistry; D013237:Stereoisomerism
chemical_list: D009439:Neuraminidase
keywords: biochemistry; enzymes; hydrolysis; neuraminidase inhibition; stereochemistry