Question

The enzyme which catalyzes the photosynthetic $C_4$ cycle is

• A. RUBP carboxylase
• B. PEP carboxylase
• C. Carbonic anhydrase
• D. None of the above

Answer 1

The correct option is B PEP carboxylase

Phosphoenolpyruvate carboxylase is also known as PEP carboxylase is an enzyme in the family of carboxy-lyases that catalyzes the addition of CO${}_2$ to phosphoenolpyruvate (PEP) to form the four-carbon compound oxaloacetate:

PEP + CO2 → oxaloacetate + Pi

This reaction is used for carbon fixation in so-called "CAM" and "C4" plants where it plays a key role in photosynthesis. The enzyme is also found in some bacteria, but not in animals or fungi .

Therefore, the correct answer is option B.