Catalyzes the oxidative decarboxylation of (S)-malate in the presence of NADP (+) and divalent metal ions, and decarboxylation of oxaloacetate. (S)-malate + NADP(+) = CO2 + NADPH + pyruvate H(+) + oxaloacetate = CO2 + pyruvate Divalent metal cations. Prefers magnesium or manganese. Homotetramer. Belongs to the malic enzymes family.