Question

What is the role of PEP carboxylase in C4 and CAM plants?

Answer 1

PEP carboxylase:

1. Phosphoenolpyruvate (PEP) is a 3-carbon compound present in mesophyll cells.
2. It acts as a primary carbon dioxide acceptor and is converted into OAA by the action of PEP carboxylase.

Role of PEP carboxylase in C4 and CAM plants:

1. In the C4 pathway, initial carbon fixation takes place in mesophyll cells and the Calvin cycle takes place in bundle-sheath cells by PEP carboxylase.
2. PEP carboxylase attaches an incoming carbon dioxide molecule to the three-carbon molecule PEP, producing oxaloacetate (a four-carbon molecule).
3. Phosphoenolpyruvate carboxylase catalyses the primary assimilation of CO₂ in Crassulacean acid metabolism (CAM) plants.
4. It is activated by phosphorylation, and this plays a major role in setting the day-night pattern of metabolism in these plants.