PEP Carboxylase

PEP carboxylase catalyzes conversion of phosphoenolpyruvate (PEP) to Oxaloacetate.

> PEP + CO 2 <=> Oxaloacetate + Pi

The reaction, which occurs in C 4 plants and bacteria, uses the high energy phosphate of PEP to drive the incorporation of a carboxyl group in order to form oxaloacetate. In C 4 plants, PEP carboxylase is located in the mesophyll cells on the external surfaces of the plant. Incorporation of CO 2 in this manner helps to shuttle CO 2 to the bundle sheath cells, where the Calvin cycle enzymes are concentrated. It also helps to avoid the wasteful photorespiration cycle due to the oxygenase activity of the CO 2 fixing enzyme, rubisco.

See also: C 4 Cycle, Bundle Sheath Cells, Calvin Cycle, Photorespiration, Rubisco