Ribuloosi15bisfosfaatti

Ribuloosi-1,5-bisfosfaatti, often abbreviated as RuBP, is a five-carbon carbohydrate molecule that plays a crucial role in photosynthesis. Specifically, it is the primary carbon dioxide acceptor in the Calvin cycle, the light-independent reactions of photosynthesis. In this process, RuBP combines with a molecule of carbon dioxide, catalyzed by the enzyme RuBisCO (ribulose-1,5-bisphosphate carboxylase/oxygenase). This initial reaction forms an unstable six-carbon compound that immediately splits into two molecules of 3-phosphoglycerate. These 3-phosphoglycerate molecules then proceed through the rest of the Calvin cycle to eventually regenerate RuBP and produce sugars. RuBP is thus a key intermediate that facilitates the fixation of atmospheric carbon dioxide into organic compounds. Its regeneration is essential for the continuous operation of the Calvin cycle and, consequently, for the production of glucose and other carbohydrates that fuel plant growth and, indirectly, most life on Earth. The continuous turnover of RuBP links the capture of light energy to the synthesis of organic matter.