Involved in myo-inositol synthesis. D-glucose 6-phosphate = 1D-myo-inositol 3-phosphate kcat is 5.2 min(-1) for D-glucose 6-phosphate. kcat is 4.8 min(-1) for NAD(+). Polyol metabolism; myo-inositol biosynthesis; myo-inositol from D-glucose 6-phosphate: step 1/2. Expressed in siliques, leaves, roots, seed endosperm, but not in embryos. Highest expression in roots. Confined to vascular tissue and hydathodes of leaves. Lethal when homozygous. Belongs to the myo-inositol 1-phosphate synthase family.