Glucose 6-phosphate (Glc6P) transporter (PubMed:15722468). Transports also inorganic phosphate, 3-phosphoglycerate, triose phosphates and, to a leser extent, phosphoenolpyruvate (PubMed:15722468). Responsible for the transport of Glc6P into plastids of heterotrophic tissues where it can be used as a carbon source for starch biosynthesis, as substrate for fatty acid biosynthesis or as substrate for NADPH generation via the oxidative pentose phosphate pathway (OPPP) (PubMed:15722468). Required for pollen maturation and embryo sac development (PubMed:15722468, PubMed:20659277). Preferentially exchanges Glc6P for ribulose-5-phosphate (Ru5P) in reconstituted yeast proteoliposomes (PubMed:32111666). May supply the substrate (Glc6P) for OPPP reactions inside peroxisomes and exchange it with the product Ru5P which leaves the organelle (PubMed:32111666). Targeted to peroxisomes via the endoplasmic reticulum. Expressed in seeds, flowers, rosette leaves, and roots, with highest levels found in stamens. Found in the root cap, in guard cells and in mesophyll cells. Expressed during the transient accumulation of starch in the developing seeds. Decline rapidly 8 days after flowering. Not detected in mature seeds. Gametophytic lethal phenotype in homozygous plants. Belongs to the TPT transporter family. GPT (TC 2.A.7.9) subfamily.