In: Biology
what enzyme does Rubisco catalyze and why is it important?
Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase), the most abundant enzyme on earth, catalyses the first major step in the fixation of carbon by adding gaseous carbon dioxide to ribulose-1,5-bisphosphate (RuBP). Which results in the formation of two molecules of 3-phosphoglyceric acid (3-PGA). Hence Rubisco is the key enzyme in CO2 assimilation, a biologically important process by which inorganic carbon enters biosphere.
This is the first step of Calvin-Benson cycle, a cycle in the carbon reactions of photosynthesis. In which the CO2 acceptor molecule (RuBP) is carboxylated by Rubisco enzyme
ribulose-1,5-bisphosphate (RuBP) ------(RUBISCO-carboxylation reaction)----------> 3-phosphoglycerate (2)
As the name suggests, ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) can catalyse two reactions namely carboxylation as well as oxygenation. The carboxylation reaction of Rubisco has already mentioned above.
The oxygenation reaction of Rubisco is present in photorespiration, also called as C2 oxidative photosynthetic carbon cycle, in which RuBP is oxygenated to yield one molecule each of 3-phosphoglycerate and 2-phospho glycolate.
ribulose-1,5-bisphosphate (RuBP) ----(RUBISCO-oxygenation)-----> 3-phosphoglycerate+2-phosphoglycolate