Gene expression and characterization of a stress-induced tyrosine decarboxylase from Arabidopsis thaliana.

Full-length tyrosine decarboxylase cDNA (TyrDC) from Arabidopsis thaliana was identified by rapid amplification of cDNA ends-PCR and isolated by RT-PCR. The TyrDC mRNA was substantially induced by drought stress and wounding, and was considerably decreased by salt stress. By using TyrDC protein fusions with green fluorescent protein, an intracellular localization to the cytoplasm was shown. Recombinant (His)(6)-TyrDC was expressed in Escherichia coli and enzymatically characterized: it exclusively catalyzed the conversion of L-tyrosine to tyramine, exhibited an optimum temperature of 50 degrees C, and an optimum pH at approximately 8.5-9. Recombinant TyrDC protein formed tetramers, as shown by blue native gel electrophoresis.