The chloroplastic, NADP-dependent form is essential for the photosynthesis C4 cycle, which allows plants to circumvent the problem of photorespiration. In C4 plants, NADP-MDH activity acts to convert oxaloacetate to malate in chloroplasts of mesophyll cells for transport to the bundle sheath cells (Probable). Plays an essential role in the regulation of catalase activity and the accumulation of a hydrogen peroxide-dependent signal by transmitting the redox state of the chloroplast to other cell compartments (PubMed:24591715). (S)-malate + NADP(+) = H(+) + NADPH + oxaloacetate Chloroplast NADP-MDH is activated upon illumination. In order to be enzymatically active, disulfide bridges on the protein must be reduced by thioredoxin which receives electrons from ferredoxin and the electron transport system of photosynthesis. Homodimer. By low temperature and high light. No visible phenotype under normal growth conditions and high-light conditions in short days. May be due to a competing acceptor splice site. Belongs to the LDH/MDH superfamily. MDH type 2 family. Truncated N-terminus.