Catalyzes the hydrolysis of fructose 1,6-bisphosphate to fructose 6-phosphate. Is likely to be involved in gluconeogenesis during growth on glycerol. Also displays a low activity toward glucose 1,6-bisphosphate, and no activity against ribulose 1,5-bisphosphate, fructose 2,6-bisphosphate, or fructose 1-phosphate. beta-D-fructose 1,6-bisphosphate + H2O = beta-D-fructose 6-phosphate + phosphate Manganese. Mg(2+), Co(2+), Ni(2+), Ca(2+), Cu(2+) and Zn(2+) cannot support activity. Competitively inhibited by low concentrations of phosphate (IC50 3.0 mM) and is also sensitive to Li(+) (IC50 70 mM). Slightly activated by KCl. The catalytic efficiency of GlpX is 3-fold higher than that of YggF, the other FBPase class 2 in E.coli. Optimum pH is 7.5-8. Carbohydrate biosynthesis; gluconeogenesis. Homodimer. By glycerol and sn-glycerol-3-phosphate. Cells lacking this gene grow normally on gluconeogenic substrates (succinate or glycerol). E.coli K12 also possesses a FBPase class 1 (Fbp), which is the primary FBPase in E.coli and probably represents the main gluconeogenic FBPase. Belongs to the FBPase class 2 family. The C-terminal part of glpX was incorrectly assigned as being part of mvrA.