| Ribulose-1,5-bisphosphate | |
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| Identifiers | |
| ChemSpider | 110238 |
| ChEBI | CHEBI:16710 |
| Jmol-3D images | Image 1 |
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| Properties | |
| Molecular formula | C5H12O11P2 |
| Molar mass | 310.09 g mol−1 |
| (verify) (what is: /?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) |
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| Infobox references | |
Ribulose-1,5-bisphosphate (RuBP) is an organic substance that is involved in photosynthesis. The anion is a double phosphate ester of the ketose (ketone-containing sugar) called ribulose. Salts of this species can be isolated, but its crucial biological function involves this colourless anion in solution. [1] To simplify the presentation, the image in the above table depicts the acid form of this anion.
The enzyme ribulose bisphosphate carboxylase oxygenase (RuBisCO) catalyzes the reaction between RuBP with carbon dioxide. The product is the highly unstable 6-carbon intermediate known as 3-keto-2-carboxyarabinitol 1,5-bisphosphate. This six-carbon intermediate decays virtually instantaneously into two molecules of glycerate 3-phosphate (G3P) (see figure). Less commonly (e.g. at high temperatures) RuBisCO catalyzes RuBP with oxygen (O2) in a process called photorespiration, a process that occurs at high temperatures in "C3 plants."
In the Calvin Cycle, RuBP is a product of the phosphorylation of ribulose-5-phosphate by ATP.
5-carbon RuBP + 1-carbon CO2 --> 6-carbon intermediate --> 2 3-PGA (3-Phosphoglyceric acid). Each (3-carbon) 3-PGA is then reduced to G3P in carbon reduction. 5 G3P = 3 RuBP. 2 G3P = 1 C6H12O6 (glucose).