Involved in the gluconeogenesis. Catalyzes stereospecifically the conversion of dihydroxyacetone phosphate (DHAP) to D-glyceraldehyde-3-phosphate (G3P). D-glyceraldehyde 3-phosphate = dihydroxyacetone phosphate kcat is 88000 min(-1) for isomerase activity with D-glyceraldehyde 3-phosphate as substrate (at pH 7.5 and 25 degrees Celsius). Carbohydrate biosynthesis; gluconeogenesis. Carbohydrate degradation; glycolysis; D-glyceraldehyde 3-phosphate from glycerone phosphate: step 1/1. Homodimer. Belongs to the triosephosphate isomerase family.