Phosphatase with a broad specificity. Its primary physiological function is to dephosphorylate 3'-phosphoadenosine 5'-phosphate (PAP) and 3'-phosphoadenosine 5'-phosphosulfate (PAPS). Thus, plays a role in mycobacterial sulfur metabolism, since it can serve as a key regulator of the sulfate assimilation pathway by controlling the pools of PAP and PAPS in the cell. To a lesser extent, is also able to hydrolyze inositol 1-phosphate (I-1-P), fructose 1,6-bisphosphate (FBP) (to fructose 6-phosphate (F-6-P)) and AMP in vitro, but this might not be significant in vivo. Glucose-1-phosphate (G-1-P), p-nitrophenyl phosphate (pNPP), and beta-glycerol phosphate (beta-GP) are also good substrates, compared to I-1-P. With much lower efficiency, can also hydrolyze inositol 2-phosphate (I-2-P) and glucose-6-phosphate (G-6-P) in vitro, but not fructose-6-phosphate (F-6-P) and trehalose-6-phosphate (T-6-P). adenosine 3',5'-bisphosphate + H2O = AMP + phosphate beta-D-fructose 1,6-bisphosphate + H2O = beta-D-fructose 6-phosphate + phosphate a myo-inositol phosphate + H2O = myo-inositol + phosphate Mg(2+). Mn(2+) can substitute for Mg(2+) for PAP phosphatase and IMPase activities, but is less efficient (50%-60% of the activity observed with Mg(2+)). PAP phosphatase and IMPase activities are inhibited by Li(+). To a lesser extent, PAP hydrolysis is also inhibited by Na(+) and K(+), with IC50 values of 150 and 250 mM, respectively, so much higher than IC50 with Li(+) (0.5 mM). Exhibits about 50% residual IMPase activity at 5 mM Li(+) and about 10% at 30 mM Li(+). Na(+) and K(+) have no significant effect on IMPase activity between 0 and 200 mM. The second-order rate constant for PAP was determined to be over 3 orders of magnitude greater than those determined for IMP and FBP. Optimum pH is 8.5-9.5 for PAP phosphatase activity, 9.3 for IMPase activity, and about 10 for FBPase activity. IMPase activity shows a dramatic decrease at low pH. In contrast, IMPase activity is highly stable at alkaline pH, with more than 60% activity remaining at pH 12. Optimum temperature is 62 degrees Celsius for IMPase activity. After preincubation at 70 degrees Celsius for 2 minutes and then being assayed at 37 degrees Celsius, more than 95% activities of IMPase and FBPase are lost. Sulfur metabolism; sulfate assimilation. Homodimer. When comparing gene expression levels of the four IMPase family genes in exponential cultures of M.tuberculosis, the level of cysQ is the highest, almost equal to sigA; impA and impC are expressed at approximately 40% of this level, while suhB is lowest, at 12% of the cysQ level. Strains lacking this gene show normal growth, do not require exogenous inositol for growth, and show no differences in levels of phosphatidylinosotol mannosides (PIMs), lipomannan (LM), lipoarabinomannan (LAM) or mycothiol (in the absence of exogenous inositol). Belongs to the inositol monophosphatase superfamily.