Discuss the behaviour of the enzymes RUBISCO under high oxygen concentration and in presence of light in `C_(3)` plants.

Explanation

The enzyme RUBISCO (Ribulose bisphosphate carboxylase) is the most important and abundant enzyme in the plant world. This enzyme initiates carboxylation of ribulose-1,5-biosphosphate to produce a transient 6-carbon compound called 2-carboxy 3-keto 1, 5-bisphosphoribitol which splits into 2 molecules of 3-phosphoglyceric acid(PGA). However, under some specific conditions, i.e, under high oxygen concentration and in presence of light, the same enzyme catalyses the combination of `O_(2)` with ribulose bisphophate. This reaction is called oxygenaton which leads to the formation of one molecules of 2-phosphoglycolic acid and one molecle of 3-phosphoglyceric acid. The two reactions, i.e., carboxylation and oxygenation, occur because of the fact that the active site of enzymes RUBISCO is the same for both reactions. The oxygenation leads to the process of photorespiration.