Synthesis of 3-phosphoglycerate producing ATP When 1,3-BPG is converted to 3-phosphoglycerate, the high-energy phosphate group of 1,3-BPG is used to synthesize ATP from ADP (see Figure 8.18). This reaction is catalyzed by phosphoglycerate kinase , which, unlike most other kinases , is physiologically reversible. Because two molecules of 1,3-BPG are formed from each glucose molecule, this kinase reaction replaces the two ATP molecules con- sumed by the earlier formation of glucose 6-phosphate and fructose 1,6-bisphosphate. [Note: This is an example of substrate-level phos- phoryl ation, in which the energy needed for the production of a high- energy phosphate comes from a substrate rather than from the electron transport chain (see J. below and p. 113 for other examples).]