Glucose 6-phosphate isomerase catalyzes the reversible interconversion of alpha-D-glucose 6-phosphate and fructose-6-phosphate. No gene has been identified in either rice or Arabidopsis thaliana that encodes an isoform of glucose-6-phosphate isomerase localized to plastids. Nevertheless, biochemical studies of embryos of Brassica napus, a species closely related to Arabidopsis, have demonstrated the existence of enzymatic activity in both cytosol and plastids (Eastman and Rawsthorne 2000), and on that basis this reaction has been annotated.
