What does the enzyme PEP carboxylase do?

1 Answer
Jan 29, 2017

Phospho enrol pyruvate (PEP) carboxylase enzyme, catalyses the addition of bicarbonate to PEP to form four carbon compound oxaloacetate and inorganic phosphate.


The three most important roles that PEP carboxylase plays in plants and bacteria metabolism are in the C4 cycle, the CAM cycle and the Citric Acid Cycle biosynthesis flux.

C4 Cycle
Some plants increase the local CO2 concentration in a process called C4 Cycle. PEP carboxylase plays the key role of binding CO2 to create oxaloacetate in the mesophyll tissue.

CAM Cycle
CAM cycle is common in organisms living in arid habitats. During night the plants take in CO2 by fixing with PEP to form oxalate through PEPcarboxylase. These are converted and stored for use during the day when light dependent reactions generate energy and reducing equivalents such as NADPH to run the Calvin cycle.

Citric Acid Cycle
PEP carboxylase is significant in non photosynthetic metabolic pathways. PEP carboxylase replenishes oxaloacetate in the Kreb's cycle. To increase flux through the cycle , some of the PEP is converted to oxaloacetate by PEP carboxylase. Since the citric acid cycle intermediates provide a hub for metabolism, increasing flux is important for the biosynthesis of many molecules.

Enzyme PEP carboxylase is found a n plants and some bacteria.