Carboxylation
The reaction in which Rubisco adds carbon dioxide to ribulose-1,5-bisphosphate, beginning carbon fixation in the Calvin cycle.
Carboxylation is the carbon-fixing reaction catalyzed by Rubisco RuBisCO The enzyme that begins carbon fixation by adding carbon dioxide to RuBP. It can also react with oxygen, initiating photorespiration. . The enzyme adds carbon dioxide to ribulose-1,5-bisphosphate, or RuBP, and the resulting unstable molecule splits into two three-carbon compounds.
Rubisco can also react with oxygen. Carbon dioxide and oxygen therefore compete at the enzyme, with carboxylation feeding the Calvin cycle and oxygenation initiating photorespiration. Their relative rates change with carbon dioxide concentration, oxygen concentration, and temperature.