Catalyzes the conjugation of the 1'-hydroxyl group of D-myo-inositol-3-phosphate (also named L-myo-inositol-1-phosphate) with a lipid tail of cytidine diphosphate diacylglycerol (CDP-DAG), forming phosphatidylinositol phosphate (PIP) and CMP. PIP is a precursor of phosphatidylinositol (PI) which is an essential lipid for mycobacteria required for formation of their cell wall (PubMed:20798167). Is essential to the survival of M.smegmatis (PubMed:10889206). 1D-myo-inositol 3-phosphate + a CDP-1,2-diacyl-sn-glycerol = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-3-phosphate) + CMP + H(+) 1,2-di-(9Z-octadecenoyl)-sn-glycero-3-cytidine-5'-diphosphate + 1D-myo-inositol 3-phosphate = 1,2-di-(9Z-octadecenoyl)-sn-glycero-3-phospho-(1D-myo-inositol-3-phosphate) + CMP + H(+) 1,2-dihexadecanoyl-sn-glycero-3-CDP + 1D-myo-inositol 3-phosphate = 1,2-dihexadecanoyl-sn-glycero-3-phospho-(1D-myo-inositol-3-phosphate) + CMP + H(+) Contains a di-nuclear catalytic Mg(2+) center. Competitively inhibited by several inositol 1-phosphate analogs, including the phosphonate analog 1-deoxy-1-phosphonomethyl-myo-inositol (Ino-C-P) (By similarity). This leads to inhibition of M.smegmatis growth (PubMed:23225597). Phospholipid metabolism; phosphatidylinositol phosphate biosynthesis. Homodimer. Allelic exchange at the pgsA chromosomal locus is achievable only when a rescue copy of the pgsA gene is provided to the bacterium, demonstrating gene essentiality. Belongs to the CDP-alcohol phosphatidyltransferase class-I family. Was orginally thought to be a phosphatidylinositol (PI) synthase.