# RuBisCO is the most abundant enzyme in the world and present in very high concentration in chloroplasts. It is required in very high concentration for Photosynthesisbecause it (1) is a very slow acting enzyme. (2) also acts as an oxygenase. (3) catalyzes a reversible reaction. (4) is degraded very rapidly..explaiin in detail...

Dear student,

RuBisCo is called RUBP carboxylase - oxygenase because the enzyme catalyses the carboxylation (the chemical process by which a carboxyl group -COOH is added) of  ribulose-1,5-bisphosphate, RuBP, a 5-carbon  compound, by carbon dioxide (a total of 6 carbons) in a two-step reaction. Sometimes the magnesium metal center of Rubisco coordinates to RuBP and oxygen instead of carbon dioxide.  Rubisco then catalyzes an oxygenase reaction. Under normal conditions the rate of the carboxylase reaction is 4 times faster than the oxygenase reaction.

It is required in very high concentration for Photosynthesis because it also acts as an oxygenase. Hence, option (2) is correct.