title: Solution structure of 5-keto-D-fructose: relevance to the specificity of hexose kinases.
abstract: 5-Keto-D-fructose (5KF) is isolated from cultures of Gluconobacter cerinus growing on D-fructose as the sole carbon source. 5KF is a substrate for hexokinase, fructokinase, and several polyol dehydrogenases. 1H and 13C nuclear magnetic resonance studies show that 5KF exists in different forms in anhydrous dimethyl-d6 sulfoxide and D2O. In dimethyl-d6 sulfoxide, 5KF exists as a spirane dimer with linked furanose and pyranose rings, similar to the structure reported for crystalline 5KF [Hassen, L., Hordvik, A., & Hove, R. (1976) J. Chem. Soc., Chem. Commun., 572-. In D2O, 5KF exists predominantly (greater than 95%) in a beta-pyranose form with the 5-keto group hydrated to form a gem-diol. 13C--1H coupling patterns, 13C relaxation measurements, and 13C deuterium-induced differential isotope shifts confirm this structure of 5KF. The phosphorylation of 5KF by fructokinase can be accounted for by an approximately 2% proportion of the beta-furanose form in solution at 25 degrees C. Both the beta-pyranose and beta-furanose forms of 5KF are proposed to be substrates for yeast hexokinase.
mesh_terms: D003903:Deuterium; D004121:Dimethyl Sulfoxide; D005631:Fructokinases / Q000378:metabolism; D005632:Fructose / Q000031:analogs & derivatives* / Q000378:metabolism; D006593:Hexokinase / Q000378:metabolism*; D046911:Macromolecular Substances; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D011548:Pseudomonadaceae / Q000032:analysis; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013816:Thermodynamics
chemical_list: D046911:Macromolecular Substances; C033856:5-ketofructose; D005632:Fructose; D003903:Deuterium; D005631:Fructokinases; D006593:Hexokinase; D004121:Dimethyl Sulfoxide