Glyceraldehyde 3 phosphate dehydrogenase (GAPDH) is well known as one of the key enzymes involved in glycolysis. As well as functioning as a glycolytic enzyme in cytoplasm, recent evidence suggests that mammalian GAPDH is also involved in a great number of intracellular proceses such as membrane fusion, microtubule bundling, phosphotransferase activity, nuclear RNA export, DNA replication, and DNA repair. During the last decade a lot of data appeared concerning the role of GAPDH in different pathologies including prostate cancer progression, programmed neuronal cell death, age related neuronal diseases, such as Alzheimer's and Huntington's disease. GAPDH is expressed in all cells. It is constitutively expressed in almost all tissues at high levels. There are however some physiological factors such as hypoxia and diabetes that increase GAPDH expression in certain cell types. GAPDH molecule is composed of four 38kDa subunits.