Photorespiration is associated with $\mathrm{C}_3$ cycle, where plant lose $\mathrm{CO}_2$ fixation because of the increase in concentrate ion of $\mathrm{O}_2$ and change the nature of activity of RuBP carboxylase-oxygenase.

$\mathrm{C}_4$ plants have evolved a mechanism to avoid loss of $\mathrm{CO}_2$. There is not a direct contact of RuBP carboxylase-oxygenase as $\mathrm{C}_3$ cycle operates in bundle sheath cells (where both temperature and oxygen level low).

$\mathrm{CO}_2$ fixation is done by another enzyme PEP carboxylase in mesophyll cells and oxaloacetate is formed which is converted to malic acid and transported to bundle sheath cells.

There, it gives off $\mathrm{CO}_2$ which is used in Calvin cycle, operating in bundle sheath cells of $\mathrm{C}_4$ plants.