Involved in the regulation of sugars and amino acids metabolisms during the night period. (S)-malate + NAD(+) = CO2 + NADH + pyruvate Divalent metal cations. Prefers magnesium or manganese. Activated by oxaloacetate (OAA), 2-ketoglutarate, succinate and fumarate as homodimer and by OAA, 2-ketoglutarate, succinate, fumarate and coenzyme A (acetyl-CoA and CoA) as heterodimer NAD-MEH. kcat is 31.1 sec(-1) for the homodimer and 39 sec(-1) for the NAD-MEH heterodimer with NAD as substrate. In the presence of coenzyme A (CoA), kcat is 40.6 sec(-1) for the NAD-MEH heterodimer with NAD as substrate. Optimum pH is 6.4 for homodimer and 6.5 for NAD-MEH heterodimer. In the presence of coenzyme A (CoA), optimum pH is 6.8 for NAD-MEH heterodimer. Homodimer. Heterodimer of two related subunits in NAD-MEH complex. Interacts with NAD-ME2. Expressed in leaves, stems, flowers, and roots (at protein level). In flowers, mostly present in sepals, stigmatic papillae, gynoecium (apical part) and filaments. Excluded from anthers (at protein level). In developing siliques, localized in the apical part and the abscission zone. In seedlings, expressed in cotyledons, hypocotyls, and root tip. Accumulates slowly in leaves as they mature, in the mesophyll and the cells that surround the vascular bundles. Accumulates during the night period (at protein level). When associated with NAD-ME2 disruption, loss of NAD-dependent malic enzyme activity associated with an altered steady-state levels of sugars and amino acids at the end of the light period. Belongs to the malic enzymes family.