alpha-D-glucose 6-phosphate = beta-D-fructose 6-phosphate Binds 1 Fe cation per subunit. Carbohydrate degradation; glycolysis; D-glyceraldehyde 3-phosphate and glycerone phosphate from D-glucose: step 2/4. Homodimer. R.meliloti has a classic glucose-6-phosphate isomerase (AC Q92SC4) and two archaeal-type glucose-6-phosphate isomerases. Belongs to the archaeal-type GPI family.