UniProt Summary: Inorganic phosphate and glucose-6-phosphate antiporter. May transport cytoplasmic glucose-6-phosphate into the lumen of the endoplasmic reticulum and translocate inorganic phosphate into the opposite direction. Independent of a lumenal glucose-6- phosphatase. May not play a role in homeostatic regulation of blood glucose levels. {ECO:0000269|PubMed:21949678}.