Catalyzes two subsequent steps in gluconeogenesis: the aldol condensation of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate (GA3P) to fructose-1,6-bisphosphate (FBP), and the dephosphorylation of FBP to fructose-6-phosphate (F6P) (PubMed:12065581, PubMed:20348906). Does not display hydrolase activity against fructose 2,6-bisphosphate, fructose 6-phosphate, fructose 1-phosphate, glucose 6-phosphate, and glucose 1-phosphate (PubMed:12065581). Exhibits only negligible activity on inositol-1-phosphate (IMP) (PubMed:15317785). Is essential for the growth of T.kodakaraensis under gluconeogenic conditions (PubMed:15317785). beta-D-fructose 1,6-bisphosphate + H2O = beta-D-fructose 6-phosphate + phosphate beta-D-fructose 1,6-bisphosphate = D-glyceraldehyde 3-phosphate + dihydroxyacetone phosphate Activity is enhanced by dithioerythritol, and is slightly inhibited by fructose 2,6-bisphosphate. AMP does not inhibit the enzyme activity. kcat is 17 sec(-1) for the FBPase activity (at 95 degrees Celsius). kcat is 7 sec(-1) for the FBPase activity (at 85 degrees Celsius). kcat is 2.9 sec(-1) for the FBPase activity (at 37 degrees Celsius). Optimum pH is 8.0. Optimum temperature is over 95 degrees Celsius. The enzyme shows a nearly linear increase in activity between 37 and 95 degrees Celsius, with a 6-fold increase between these temperatures. Is highly thermostable, displaying a half-life of 150 minutes in boiling water. Carbohydrate biosynthesis; gluconeogenesis. Homooctamer; dimer of tetramers. High levels of transcripts are detected in cells grown on pyruvate or amino acids, whereas no transcription is detected when starch is present in the medium, revealing a sugar-repressed gene expression. Consists of a single catalytic domain, but remodels its active-site architecture via a large structural change to exhibit dual activities. Cells lacking this gene cannot grow under gluconeogenic conditions while glycolytic growth is unimpaired, and the gene disruption results in the complete abolishment of intracellular FBPase activity. Belongs to the FBP aldolase/phosphatase family.