beta-D-fructose 1,6-bisphosphate + H2O = beta-D-fructose 6-phosphate + phosphate Binds 2 magnesium ions per subunit. Subject to complex allosteric regulation. The enzyme can assume an active R-state, or an inactive T-state. Intermediate conformations may exist. Activated by three-carbon carboxylic acids, phosphorylated three-carbon carboxylic acids and sulfate. Strongly activated by phosphoenolpyruvate and citrate. Inhibited by AMP, which affects the turnover of bound substrate and not the affinity for substrate. Allosterically inhibited by glucose 6-phosphate. AMP and glucose 6-phosphate act synergistically as allosteric inhibitors. Phosphoenolpyruvate antagonizes inhibition by AMP and glucose 6-phosphate. Fructose 2,6-bisphosphate acts as competitive inhibitor. Carbohydrate biosynthesis; gluconeogenesis. Homotetramer. Phosphoenolpyruvate stabilizes the homotetramer. Belongs to the FBPase class 1 family.