Sucrose phosphate synthase, a key enzyme for sucrose biosynthesis in plants: protein purification from corn leaves and immunological detection

We have purified the protein for the enzyme sucrose phosphate synthase (SPS) from corn (Zea mays) leaves. Partially purified SPS protein was used to generate specific monoclonal antibodies. The following immunoaffinity chromatography allowed the isolation of pure SPS protein. The apparent molecular mass of the SPS polypeptide is 138 kilodaltons. By immunoblot, an SPS antigen was found to accumulate in mature leaves. SPS protein levels remain constant during the day/night cycle. The observed diurnal fluctuation of extractable enzyme activity, therefore, must be caused by modification of the specific activity of SPS in vivo.