Virulence factor that plays an important role in blocking phagosome-lysosome fusion and thus participates in the intracellular survival of the pathogen (PubMed:15753315, PubMed:23923000). Acts as a phosphatase that dephosphorylates phosphatidylinositol 3-phosphate (PI3P), a membrane trafficking regulatory lipid essential for phagosomal acquisition of lysosomal constituents (PubMed:15753315). Therefore, SapM eliminates PI3P from the phagosomal membrane by catalyzing its hydrolysis, and thus contributes to inhibition of phagosome maturation (PubMed:15753315). Also interferes with autophagy: SapM blocks autophagosome-lysosome fusion in macrophages by binding to the small GTPase RAB7, which prevents RAB7 from being involved in this process and thus negatively regulates autophagy flux (PubMed:25896765). In vitro, displays phosphatase activity with broad specificity; can dephosphorylate a variety of phosphoester substrates, with the highest activity against phosphoenolpyruvate, glycerophosphate, GTP, NADPH, phosphotyrosine and trehalose-6-phosphate (PubMed:11073936). In contrast, the enzyme exhibits poor activity against glucose-6-phosphate, phosphothreonine, and a number of nucleotides (NADP, ATP, AMP, and GMP) (PubMed:11073936). a phosphate monoester + H2O = an alcohol + phosphate a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-3-phosphate) + H2O = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol) + phosphate Phosphatase activity is inhibited in vitro by low concentrations of several heavy metals (zinc chloride, sodium molybdate, magnesium chloride, and copper sulfate) and moderately high concentrations (>8 mM) of EDTA. Optimum pH is 6.5-7.5. Significant phosphatase activity is observed between pH 5.5 and 8.0. Monomer (PubMed:11073936). SapM interacts with host RAB7 via its C-terminus (PubMed:25896765). It remains to be determined how SapM, once secreted into the phagosomal lumen, gains access to PI3P within the cytofacial membrane leaflet. It is possible that SapM is exported to the cytosolic side, or alternatively there may be a mechanism for PI3P presentation to SapM remaining on the luminal side. The C-terminus of SapM is required for interaction with RAB7 and SapM-mediated autophagy block. Strain lacking this gene is defective in the arrest of phagosomal maturation as well as for growth in human THP-1 macrophages. The mutant strain is severely attenuated for growth in the lungs and spleen of guinea pigs and has a significantly reduced ability to cause pathological damage in the host when compared with the parental strain. Also, the guinea pigs infected with the mutant strain exhibit a significantly enhanced survival when compared with M.tuberculosis infected animals.