Rubisco and PEP case are the two important enzymes of C3 and C4 pathways. Rubisco is the primary CO₂ receiver in C3 facilities while PEP case is the main CO₂ receiver for C4 facilities.

Rubisco’s role: The Rubisco RUBP carboxylase is also called oxygenase. It has carboxylase as well as oxygenase functions, as the name suggests. The enzyme has more carbon dioxide potential than oxygen affinity. Some of the enzyme, however, is linked to oxygen

C3 plants a photorespiration process. Photo vacuum is a wasteful process because it does not produce a product that is useful for plants.In addition, carbon fastening in C3 plants is also reduced.

PEP case Role: this is the primary accepter of carbon dioxide in C4 plants. In these plants, however, Rubisco is also available. A4-carbon oxaloacetic (OAA) compound PEP case binds to carbon dioxide eventually becomes carbon dioxide.

Carbon dioxide is lastly produced in the cycle of Calvin. Keep in mind that both C3 and C4 plants use the Calvin Cycle.