title: Isotope-tapping experiments with rabbit liver fructose bisphosphatase.
abstract: Isotope-trapping experiments with mental-free rabbit liver fructose 1,6-bisphosphatase have shown that enzyme-bound D-fructose 1,6-bisphosphate completely dissociates prior to enzyme turnover initiated by Mn2+ as the catalytic metal. The exchange rate of the binary enzyme-D-fructose 1,6-bisphosphate complex with the substrate pool is, therefore, more rapid than its conversion to products, suggesting that structural Mn2+ is necessary for productive substarate binding. Rapid-quench isotope-trapping experiments confirm the requirement for structural Mn2+ ions for productive binding to occur. These experiments also show that an ordered formation of the enzyme-Mn2+ s-D-fructose 1,6-bisphosphate ternary complex which features metal-ion addition prior to substrate constitutes a catalytically competent pathway in the mechanism of fructose 1,6-bisphosphatase and that all four subunits are active in a single turnover event.
mesh_terms: D000818:Animals; D001665:Binding Sites; D002384:Catalysis; D006597:Fructose-Bisphosphatase / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D046911:Macromolecular Substances; D008345:Manganese / Q000494:pharmacology*; D010761:Phosphorus Radioisotopes; D011817:Rabbits
chemical_list: D046911:Macromolecular Substances; D010761:Phosphorus Radioisotopes; D008345:Manganese; D006597:Fructose-Bisphosphatase