PGK2 and obesity due to melanocortin 4 receptor deficiency: Among these genes, lactate dehydrogenase C (LDHC), phosphoglycerate kinase 2 (PGK2), and glyceraldehyde-3-phosphate dehydrogenase spermatogenic (GAPDHS) encode three testis-specific glycolytic enzymes that are essential for sperm ATP production and are markers of the functional role of glycolysis in obesity-induced sperm motility abnormalities.