May play an important role in regulating the switch between different pathways for energy production during spermiogenesis and in the spermatozoon. Required for sperm motility and male fertility. D-glyceraldehyde 3-phosphate + NAD(+) + phosphate = (2R)-3-phospho-glyceroyl phosphate + H(+) + NADH Carbohydrate degradation; glycolysis; pyruvate from D-glyceraldehyde 3-phosphate: step 1/5. Homotetramer. Testis specific. First expressed at day 20 in post-meiotic germ cells. Levels increase until day 24 and then remain constant during maturity. The testis-specific N-terminal extension mediates tight association with the cytoskeletal fibrous sheath of the spermatozoa flagellum, possibly via interchain disulfide-bonding of Cys-33 with sheath components. Mice display greatly reduced ATP levels in sperm, severely impaired sperm motility and are infertile. Belongs to the glyceraldehyde-3-phosphate dehydrogenase family.