GAPDH, or glyceraldehyde-3-phosphate dehydrogenase, is an enzyme that plays a crucial role in the process of glycolysis, which is the breakdown of glucose to produce energy. It catalyzes the conversion of glyceraldehyde-3-phosphate into 1,3-bisphosphoglycerate, a key step in energy production within cells. In addition to its metabolic functions, GAPDH is also involved in various cellular processes, including DNA repair and apoptosis. Due to its essential role in metabolism, GAPDH is often used as a housekeeping gene in molecular biology experiments to normalize data in gene expression studies.