NAD(+) + sn-glycerol 3-phosphate = dihydroxyacetone phosphate + H(+) + NADH Phospholipid metabolism; alpha-glycerophosphate cycle. Homodimer. Isoform GPDH-1 is predominant in thorax and isoform GPDH-3 in abdomen. Isoform GPDH-2 and isoform GPDH-3 are expressed in both larvae and adults. Isoform GPDH-1 is expressed only in adults. There are two common alleles; fast and slow. The sequence of fast is shown here. Belongs to the NAD-dependent glycerol-3-phosphate dehydrogenase family.