Pyruvate   carboxylase   is a mitochondrial   matrix enzyme whereas the other enzymes of gluconeogenesis are situated outside the mitochondrion. Thus oxaloacetate are produced by pyruvate   carboxylase,   needs exiting the mitochondrion. Furthermore, the inner mitochondrial membrane is not permeable to this compound. Thus oxaloacetate is converted to malate inside the mitochondrion by mitochondrial malate dehydrogenase, the malate is transported by the mitochondrial membrane by a special transport protein and then the malate is converted back to oxaloacetate in the cytoplasm by a cytosolic malate dehydrogenase.