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 (By similarity). (S)-malate + NADP(+) = CO2 + NADPH + pyruvate H(+) + oxaloacetate = CO2 + pyruvate Divalent metal cations. Prefers magnesium or manganese. kcat is 151.3 sec(-1) with NADP as substrate (at pH 7.5). Photosynthesis; C3 acid pathway. Homodimer and homotetramer. Expressed in leaves, stems, flowers and roots, mainly in vascular system. In roots, present in the stele, including the vascular tissue and the pericycle, mainly at emerging lateral roots and at root tips. During embryogenesis, present in the endosperm and the embryo at all developmental stages, including the seed attachment point and the integuments. Also detected in siliques. During germination, first confined to the radicle to later approaches the meristematic region. Finally present in the whole root. Expressed in cotyledons and primary leaves. In opened flowers, present in sepals, stigma, filaments, and pollen. Belongs to the malic enzymes family. Truncated N-terminus.