Key enzyme in myo-inositol biosynthesis pathway that catalyzes the conversion of glucose 6-phosphate to 1-myo-inositol 1- phosphate in a NAD-dependent manner (PubMed:15024000, PubMed:23902760). Rate-limiting enzyme in the synthesis of all inositol-containing compounds (PubMed:15024000). {ECO:0000269|PubMed:15024000, ECO:0000269|PubMed:23902760}. This is the function of ENSG00000105655 (ISYNA1, inositol-3-phosphate synthase 1).