In the cytoplasm, catalyzes the conversion of glucose-6-phosphate to fructose-6-phosphate, the second step in glycolysis, and the reverse reaction during gluconeogenesis (PubMed:28803808). Besides it's role as a glycolytic enzyme, also acts as a secreted cytokine: acts as an angiogenic factor (AMF) that stimulates endothelial cell motility (PubMed:11437381). Acts as a neurotrophic factor, neuroleukin, for spinal and sensory neurons (PubMed:3352745, PubMed:11004567). It is secreted by lectin-stimulated T-cells and induces immunoglobulin secretion (PubMed:3352745, PubMed:11004567). alpha-D-glucose 6-phosphate = beta-D-fructose 6-phosphate Strongly inhibited by erythrose 4-phosphate. Carbohydrate degradation; glycolysis; D-glyceraldehyde 3-phosphate and glycerone phosphate from D-glucose: step 2/4. Homodimer; in the catalytically active form (PubMed:11371164, PubMed:12054796, PubMed:12777791). Monomer in the secreted form (PubMed:11371164, PubMed:12054796, PubMed:12777791). Phosphorylation at Ser-185 by CK2 has been shown to decrease enzymatic activity and may contribute to secretion by a non-classical secretory pathway. ISGylated. The disease is caused by variants affecting the gene represented in this entry. Belongs to the GPI family. Phosphoglucose isomerase entry