title: Theoretical examination of the mechanism of aldose-ketose isomerization.
abstract: Two mechanisms for an aldose-ketose isomerization have been examined using high level ab initio and semiempirical molecular orbital methods. The proton transfer pathway via an enediol intermediate is shown to be favored in the absence of a metal ion, while the hydride transfer pathway becomes favored in the presence of a metal ion. Our calculations explain why the proton transfer pathway is operative in most aldose-ketose isomerization reactions. These calculations also provide further support for the previously proposed metal ion-mediated hydride transfer mechanism for xylose isomerase.
authors.affiliation: 152 Davey Laboratory, Department of Chemistry, Pennsylvania State University, University Park 16802.
authors.forename: Y J
authors.initials: YJ
authors.lastname: Zheng
authors.forename: K M
authors.initials: KM
authors.lastname: Merz
authors.forename: G K
authors.initials: GK
authors.lastname: Farber
mesh_terms: D000447:Aldehydes / Q000737:chemistry*; D019747:Aldose-Ketose Isomerases; D002238:Carbohydrate Epimerases; D002384:Catalysis; D007536:Isomerism; D007661:Ketoses / Q000737:chemistry*; D008432:Mathematical Computing; D008956:Models, Chemical; D008968:Molecular Conformation; D009005:Monosaccharides / Q000737:chemistry*; D011522:Protons; D012984:Software; D014305:Triose-Phosphate Isomerase
chemical_list: D000447:Aldehydes; D007661:Ketoses; D009005:Monosaccharides; D011522:Protons; D002238:Carbohydrate Epimerases; D019747:Aldose-Ketose Isomerases; D014305:Triose-Phosphate Isomerase; C023298:xylose isomerase