Crystallization of an NADP+-dependent malic enzyme from rat liver

Abstract Crystals of a tetrameric NADP + -dependent malic enzyme from rat liver have been grown in the presence of NADP + using the hanging-drop method of vapour diffusion with ammonium sulphate as the precipitant. Measurement of the crystal density and calculation of the values of V m for different numbers of polypeptide chains in the unit cell indicate that the asymmetric unit of the crystal contains a complete tetramer, allowing the application of non-crystallographic symmetry to the determination of the molecular structure of this enzyme. This structure would provide only the second example for an enzyme involved in oxidative decarboxylation, the other being 6-phosphogluconate dehydrogenase. In addition, then, to providing an insight into the structure-function relationship in malic enzyme, the successful structure determination would permit valuable comparisons to be made between these two and other enzymes with this catalytic activity.