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. Optimum pH is 7.8-8.1. Homotetramer. Expressed in all tissues tested including liver, placenta and white adipose tissue. Belongs to the malic enzymes family.