title: UDP-galactose 4-epimerase from Escherichia coli: existence of a catalytic monomer.
abstract: UDP-galactose 4-epimerase from Escherichia coli is a homodimer of molecular mass 39 kDa/subunit and requires NAD as a co-factor. X-ray crystallographic studies indicate two pyridine nucleotide co-factor-binding sites of the dimeric molecule situated in a symmetry-oriented manner. Size-exclusion HPLC of an equilibrium intermediate at 3 M urea suggests a monomeric holoenzyme structure that is catalytically active. Ultracentrifugal studies of the native enzyme in a 5-20% sucrose gradient at low protein concentration also indicate existence of a catalytic monomer. The monomer resembles the dimeric protein in stability and most of its physico-chemical properties.
authors.affiliation: Indian Institute of Chemical Biology, Calcutta.
authors.forename: S
authors.initials: S
authors.lastname: Nayar
authors.forename: D
authors.initials: D
authors.lastname: Bhattacharyya
mesh_terms: D000817:Anilino Naphthalenesulfonates; D001665:Binding Sites; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D018360:Crystallography, X-Ray; D004789:Enzyme Activation; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology*; D005456:Fluorescent Dyes; D009994:Osmolar Concentration; D011489:Protein Denaturation; D014534:UDPglucose 4-Epimerase / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism*
chemical_list: D000817:Anilino Naphthalenesulfonates; D005456:Fluorescent Dyes; C027132:1-anilino-8-naphthalenesulfonate; D014534:UDPglucose 4-Epimerase