Catalyzes the decarboxylation of malate to pyruvate (PubMed:12949160, PubMed:16788182). Can use NAD and NADP, but with a strong preference for NAD (PubMed:12949160, PubMed:16788182). 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. Induced in the presence of malate via the two-component system MalK/MalR. The regulator MalR binds to the promoter region of maeA. Is not subject to carbon catabolite repression. Mutant can use malate, succinate plus glutamate or glucose as efficiently as the wild-type strain (PubMed:12949160, PubMed:16788182). The ATP concentrations in the mutant grown in minimal medium with glucose are similar to the wild-type level. ATP concentrations decrease by about 10% 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.