Photosynthetic tissue of these plants contains both Pep case and RuBP carboxylase. During photosynthesis, most plants use the enzyme RuBP carboxylase to capture carbon dioxide during the day. During the night, when stomata are open, CO2 is fixed by Pep case to form malic acid, which accumulates in plant tissues. In this way, they coordinate with each other and photosynthesis occur.