Involved in the glycerol metabolism. Catalyzes stereospecifically the conversion of dihydroxyacetone phosphate (DHAP) to D-glyceraldehyde-3-phosphate (G3P). D-glyceraldehyde 3-phosphate = dihydroxyacetone phosphate Polyol metabolism; glycerol degradation. Homodimer. Repressed by GolR. Belongs to the triosephosphate isomerase family.