Cytosolic phosphoglycerate kinase (PGK) catalyzes the reaction of ADP and 1,3-bisphosphoglycerate (1,3BPG) to form D glyceraldehyde 3-phosphate (3PG) and ATP. The active form of the enzyme is a monomer and requires Mg++ (Yoshida and Watanabe 1972; Huang et al. 1980a,b). This is the first substrate level phosphorylation reaction in glycolysis. Two PGK isoforms are known: PGK1 is widely expressed in the body while PGK2 (Chen et al. 1976; McCarrey & Thomas 1987) appears to be confined to sperm cells.