Ribulose 1,5-bisphosphate
Ribulose 1,5-bisphosphate is an organic substance that is involved in photosynthesis. It is a colourless anion, a double phosphate ester of the ketopentose called ribulose. Salts of RuBP can be isolated, but its crucial biological function happens in solution. To simplify the presentation, the image in the table depicts the acid form of this anion.Role in photosynthesis
The enzyme ribulose catalyzes the reaction between RuBP and carbon dioxide. The product is the highly unstable six-carbon intermediate known as 3-keto-2-carboxyarabinitol 1,5-bisphosphate. This six-carbon intermediate decays virtually instantaneously into two molecules of 3-phosphoglycerate . RuBisCO also catalyzes RuBP with oxygen in a process called photorespiration, a process that is more prevalent at high temperatures. During photorespiration RuBP combines with to become 3-PGA + phosphoglycolic acid. In the Calvin cycle, RuBP is a product of the phosphorylation of ribulose-5-phosphate by ATP.
