Catalyzes the decarboxylation of malate to pyruvate. Is specific for NAD, cannot use NADP. Can also catalyze the decarboxylation of oxaloacetate (PubMed:16788182). Involved in keeping the ATP levels high (PubMed:23136871). (S)-malate + NAD(+) = CO2 + NADH + pyruvate H(+) + oxaloacetate = CO2 + pyruvate Divalent metal cations. Weakly expressed in glucose or malate minimal medium. Mutant can use either a gluconeogenic carbon source or glucose as efficiently as the wild-type strain (PubMed:16788182). The ATP concentrations in the mutant grown in minimal medium with glucose are similar to the wild-type level. ATP concentrations slightly decrease in malate minimal medium. The mleA-maeA-malS triple mutant shows a decrease in ATP concentrations by about 20% and a moderate growth defect (PubMed:23136871). NADPH overproduction is roughly halved in the deletion mutant (PubMed:33824210). Belongs to the malic enzymes family.