Plastidial NADP-malic enzymes from grasses: Unraveling the way to the C4 specific isoforms

► Plastidial NADP-MEs from sorghum (C4) and rice (C3) were characterized. ► NADP-MEs biochemical properties are closely connected with their functional roles. ► Sorghum photosynthetic NADP-ME is regulated by redox conditions and malate levels. ► Rice plastidial NADP-ME responds to malate levels while is not redox-modulated. ► A small group of residues may explain the special features of C4 enzymes.