Phosphatase with broad specificity; it can dephosphorylate fructose 1,6-bisphosphate (FBP) and inositol-1-phosphate (IMP). However, while possessing a high FBPase activity in vitro, does not participate in gluconeogenesis in vivo. beta-D-fructose 1,6-bisphosphate + H2O = beta-D-fructose 6-phosphate + phosphate a myo-inositol phosphate + H2O = myo-inositol + phosphate kcat is 23.4 sec(-1) for FBPase activity (at 85 degrees Celsius). FBPase activity is 5-fold higher than the IMPase activity. Homodimer. Constitutively expressed, at a very weak level. Disruption of this gene does not lead to any detectable phenotypic changes regarding the growth under gluconeogenic conditions (medium supplemented with pyruvate) and glycolytic conditions (medium supplemented with soluble starch). Is not able to complement the defect of the fbp deletion under gluconeogenic conditions, probably due to insufficient transcription. Belongs to the inositol monophosphatase superfamily. FBPase class 4 family.