Correct option is B
EXPLANATION-
Statement A: Light activates PEPCase kinase in C4 plants.
This is correct. In C4 plants, light triggers the activation of PEPCase kinase, which phosphorylates PEPCase. This phosphorylation increases the activity of PEPCase and reduces its sensitivity to feedback inhibitors like malate.
Statement B: Phosphorylation inactivates PEPCase in C4 plants while it activates the enzyme in CAM plants.
This statement is incorrect. In both C4 and CAM plants, phosphorylation activates PEPCase rather than inactivates it. Phosphorylation protects the enzyme from inhibition by malate, increasing its activity.
Statement C: PEPCase kinase gets activated by light in CAM plants.
This is incorrect. In CAM plants, the regulation of PEPCase kinase is generally not light-dependent as it is in C4 plants. The phosphorylation status of PEPCase in CAM plants is mainly regulated by the circadian rhythm, i.e., it changes depending on the time of day, rather than directly by light.
Statement D: Phosphorylated PEPCase is less sensitive to malate.
This is correct. Phosphorylation of PEPCase reduces its sensitivity to malate, a feedback inhibitor, allowing the enzyme to remain active even when malate concentrations are high. This regulation helps optimize carbon fixation.
So, the correct option (b) - A and D
