title: Stereochemistry of an alpha, beta-elimination reaction by D-glucosaminate dehydratase.
abstract: The proton NMR analysis of D-glucosaminate dehydratase reaction in D2O revealed the incorporation of a deuterium atom at C-3 carbon of the product, 2-keto-3-deoxy-D-gluconate. Based on the chemical shift of C-3 proton of the product and the coupling constant characteristic for the C-3 and C-4 axial-axial coupling in the 2C5 pyranose conformation, the deuterium is in the pro-S position. Thus, the dehydration of D-glucosaminate by the enzyme proceeds in a retention mode at C-3 carbon. Kinetic parameters show that the rate-determining step is the abstraction of alpha-proton from the substrate.
mesh_terms: D003903:Deuterium; D005942:Gluconates / Q000378:metabolism; D005944:Glucosamine / Q000031:analogs & derivatives / Q000378:metabolism; D006836:Hydro-Lyases / Q000378:metabolism*; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008968:Molecular Conformation; D012231:Rhizobium / Q000201:enzymology
chemical_list: D005942:Gluconates; C002957:2-keto-3-deoxygluconate; C035547:glucosaminic acid; D003903:Deuterium; D006836:Hydro-Lyases; C018870:aminodeoxygluconate dehydratase; D005944:Glucosamine