Glucose 1,6-bisphosphate synthase using 1,3-bisphosphoglycerate as a phosphate donor and a series of 1-phosphate sugars, including glucose 1-phosphate, mannose 1-phosphate, ribose 1-phosphate and deoxyribose 1-phosphate, as acceptors (PubMed:17804405). In vitro, also exhibits very low phosphopentomutase and phosphoglucomutase activity which are most probably not physiologically relevant (PubMed:17804405). (2R)-3-phospho-glyceroyl phosphate + alpha-D-glucose 1-phosphate = (2R)-3-phosphoglycerate + alpha-D-glucose 1,6-bisphosphate + H(+) (2R)-3-phospho-glyceroyl phosphate + alpha-D-glucose 6-phosphate = (2R)-3-phosphoglycerate + alpha-D-glucose 1,6-bisphosphate + H(+) (2R)-3-phospho-glyceroyl phosphate + alpha-D-ribose 1-phosphate = (2R)-3-phosphoglycerate + alpha-D-ribose 1,5-bisphosphate + H(+) (2R)-3-phospho-glyceroyl phosphate + 2-deoxy-alpha-D-ribose 1-phosphate = (2R)-3-phosphoglycerate + 2-deoxy-alpha-D-ribose 1,5-bisphosphate + H(+) (2R)-3-phospho-glyceroyl phosphate + alpha-D-mannose 1-phosphate = (2R)-3-phosphoglycerate + alpha-D-mannose 1,6-bisphosphate + H(+) Belongs to the phosphohexose mutase family.