The affinity of rabbit muscle fructose-bisphosphatase for fructose bisphosphate

This paper reports that microM concentrations of fructose bisphosphate are titrated by rabbit muscle fructose-bisphosphatase (D-fructose-1,6-bisphosphate 1-phosphohydrolase, EC 3.1.3.11) when the enzyme concentration is varied in the range which secures measurable initial velocities of reaction: a result that can only be explained by supposing that the enzyme has a greater affinity for fructose bisphosphate than suggested by Fernando, J., Enser, M., Pontremoli, S. and Horecker, B.L. (1968) Arch. Biochem. Biophys. 126, 599-606. The results also suggest that the keto form of the substrate may be the preferred configuration and that the enzyme is inhibited by magnesium-bound fructose bisphosphate.