(2R)-3-phospho-glyceroyl phosphate + alpha-D-ribose 1-phosphate = alpha-D-ribose 1,5-bisphosphate + (2R)-3-phosphoglycerate + H(+)
(2r)-3-phospho-glyceroyl phosphate + alpha-d-ribose 1-phosphate = alpha-d-ribose 1,5-bisphosphate + (2r)-3-phosphoglycerate + h(+)