title: The enzymic synthesis of ribose-1,5-bisphosphate: studies of its role in metabolism.
abstract: Ribose-1,5-bisphosphate is synthesized in a reaction that uses ribose-1(or 5)-P as the phosphoryl acceptor and the acyl-P of 3-phosphoglyceryl phosphate as the donor. Glucose-1,6-bisphosphate is synthesized in a similar reaction. The relative activity with the two substrates remains unchanged over almost 300-fold purification of the enzyme, indicating that glucose-1,6-bisphosphate synthase catalyzes both reactions. The relative V/Km values for alternative phosphoryl acceptors are ribose-1-P (1); glucose-1-P (0.30); mannose-1-P and ribose-5-P (0.11); glucose-6-P (0.10); 2-deoxyglucose-6-P (0.03); and 2-deoxyribose-5-P (0.02). Fructose-1- and 6-phosphates are not substrates. The synthesis of both ribose-1,5-bisphosphate and glucose-1,6-bisphosphate is inhibited by physiologically significant levels of fructose-1,6-bisphosphate, glycerate-2,3-bisphosphate, glycerate-3-phosphate, citrate, and inorganic phosphate. Ribose-1,5-bisphosphate is a strong activator of brain phosphofructokinase.
mesh_terms: D000818:Animals; D001921:Brain / Q000378:metabolism; D004789:Enzyme Activation; D066298:In Vitro Techniques; D051379:Mice; D010428:Pentosephosphates / Q000096:biosynthesis*; D010732:Phosphofructokinase-1 / Q000378:metabolism; D010770:Phosphotransferases / Q000378:metabolism; D013379:Substrate Specificity
chemical_list: D010428:Pentosephosphates; C050562:ribose-1,5-bisphosphate; D010770:Phosphotransferases; C050587:ribose-1,5-diphosphate synthase; D010732:Phosphofructokinase-1