Characterization of yeast fructose-2,6-bisphosphate 6-phosphatase

AbstractTo obtain information on the biological significance of yeast fructose-2,6-bisphosphate 6-phosphatase, kinetic data of the purified enzyme [(1987) Eur. J. Biochem. 164, 27–30] have been measured. Maximal activity was found between Ph 6 and 7, the apparent Michaelis constant with fructose 2,6-bisphosphate was 7.2 μM at Ph 6.0 and 79 μm at Ph 7.0. Concentrations required for 50% inhibition of the enzyme at Ph 6.0 were 8 μm Fru2P, 45 μm G1c6P, 80 μm Fru6P and 200 μm inorganic phosphate. The known intracellular steady-state level of about 10 μm fructose 2,6-bisphosphate in the presence of glucose is likely to be the result of a balance between the rapid synthesis of fructose 2,6-bisphosphate catalyzed by 6-phosphofructose 2-kinase and a fructose 2,6-bisphosphate degrading activity. The biological function of fructose-2,6-bisphosphate 6-phosphatase with an apparent Michaelis constant between 7 and 79 μm fructose 2,6-bisphosphate at Ph 6–7 is therefore suggested to participate in the maintenance of a steady-state level of fructose 2,6-bisphosphate in a concentration range that fits well with the Michaelis constant of the enzyme