2 METHODS FOR ENZYMATIC 4-C-14-LABELING O F L-MALATE

4-C-Labeled malate, which is widely used for studying the kinetic prop erties of enzymic systems and supramolecular complexes containing mala te dehydrogenase, may be used for the synthesis of 4-C-labeled L-aspar tic acid. L-[4-C-14]Malate was synthesized in coupled enzymic reaction s of two types using maize leaf phospho(enol)pyruvate carboxylase and NAD(+)-malic enzyme from Amaranthus retroflexus leaves and purified by ion-exchange or paper chromatography. The synthesized [4-C-14]malate (97% purity) displayed a specific radioactivity of 1.7 Ci/mol.