PURIFICATION AND PROPERTIES OF A D-FRUCTOSE 1,6-BISPHOSPHATASE FROM SACCHAROMYCES-CEREVISIAE

Fructose 1,6-bisphosphatase (EC 3.1.3.11) from Saccharomyces cerevisiae has been purified to homogeneity. A molecular weight of 115,000 has been obtained by gel filtration. The enzyme appears to be a dimer with identical subunits. The apparent Km for fructose bisphosphatase varies with the Mg2+ concentration of the enzyme, being 1 × 10-6 m at 10 mm Mg2+ and 1 × 10-5 m at 2 mm Mg2+. Other phosphorylated compounds are not significantly hydrolyzed by the enzyme. An optimum pH of 8.0 is exhibited by the enzyme. This optimum is not changed by addition of EDTA. AMP inhibits the enzyme with a Ki of 8.0 × 10-5 m at 25 °C. The inhibition is temperature dependent, the value of Ki increasing with raising temperature. 2-Deoxy-AMP is also inhibitory with a Ki value at 25 °C of 1.6 × 10-4 m. An ordered uni-bi mechanism has been deduced for the reaction with phosphate leaving the enzyme as the first product and the fructose 6-phosphate as the second one. © 1979.