Question

Name the two important enzymes of $C4$ pathway, and explain their role in fixing $C{O}_2$ ?

Answer 1

PEP carboxylase :

In $C_4$ pathway, $PEP$ carboxylase is the primary enzyme that fixes the atmospheric $C{O}_2$ in the mesophyll cells.
$C{O}_2$ in the form of $HC{O}_3$- reacts with phosphoenol pyruvate $\left(PEP\right)$ and forms Oxaloacetate $\left(OAA\right)$, a four-carbon product. This reaction is catalyzed by $PEP$ carboxylase.

RubisCO :

$OAA$ formed in the mesophyll cells is converted to malic acid and is transferred to the bundle sheath. The malic acid produces carbon dioxide and pyruvate. Carbon dioxide further enters the Calvin cycle. RubisCo is the primary enzyme that catalyzes the reaction that fixes carbon dioxide and forms $PGA$ in the Calvin cycle.
In the $C4$ pathway the Calvin cycle occurs in the bundle sheath cells as the enzyme RubisCo is present in the bundle sheath cells.