title: The stereochemical course of the ribulose-5-phosphate kinase-catalyzed reaction.
abstract: Spinach-leaf ribulose-5-phosphate kinase catalyzes the reaction of (Rp)-[beta, gamma-18O, gamma-18O]adenosine 5'-(3-thiotriphosphate) with ribulose 5-phosphate to form ribulose 1-[18O]phosphorothioate 5-phosphate. This product is incubated with CO2, Mg2+, and ribulose-bisphosphate carboxylase to form the [18O]phosphorothioate of D-glycerate. Reduction of this material using phosphoglycerate kinase/ATP, glyceraldehyde-3-phosphate dehydrogenase/NADH, triose-phosphate isomerase, and glycerol-phosphate dehydrogenase/NADH produces glycerol 3-[18O]phosphorothioate, which is subjected to ring closure using diethylphosphorochloridate. This in-line reaction produces a diastereoisomeric mixture of glycerol 2,3-cyclic phosphorothioates. 31P NMR spectroscopy was used to analyze the 18O content of the products. The anti-diastereoisomer, which is the major isomer formed and corresponds to the downfield 31P NMR signal (Pliura, D.H., Schomburg, D., Richard, J.P., Frey, P.A., and Knowles, J.R. (1980) Biochemistry 19, 325-329), retains the 18O label. This observation indicates that the ribulose-5-phosphate kinase reaction proceeds with inversion of configuration at phosphorus. The reaction is, therefore, unlikely to involve the participation of a covalent phosphoryl-enzyme intermediate.
mesh_terms: D005994:Glycerophosphates / Q000378:metabolism; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D009943:Organophosphorus Compounds / Q000378:metabolism; D009946:Organothiophosphorus Compounds; D010103:Oxygen Isotopes; D010944:Plants / Q000201:enzymology; D011485:Protein Binding; D012273:Ribulose-Bisphosphate Carboxylase / Q000302:isolation & purification / Q000378:metabolism*; D013237:Stereoisomerism
chemical_list: D005994:Glycerophosphates; D009943:Organophosphorus Compounds; D009946:Organothiophosphorus Compounds; D010103:Oxygen Isotopes; C043406:glycerol 2,3-cyclic phosphorothioate; C024131:glycerol 3-phosphorothioate; D012273:Ribulose-Bisphosphate Carboxylase