The chloroplastic ME isoform decarboxylates malate shuttled from neighboring mesophyll cells. The CO(2) released is then refixed by ribulose-bisphosphate carboxylase. This pathway eliminates the photorespiratory loss of CO(2) that occurs in most plants. (S)-malate + NADP(+) = CO2 + NADPH + pyruvate H(+) + oxaloacetate = CO2 + pyruvate Divalent metal cations. Prefers magnesium or manganese. Photosynthesis; C3 acid pathway. Homotetramer. Belongs to the malic enzymes family.