Pyruvate decarboxylase (EC 4.1.1.1) from Zymomonas mobilis purified to homogeneity by using dye-ligand and ion-exchange chromatography. Antibodies produced against the enzyme and the amino-terminal sequence obtained for the pure enzyme were used to select and confirm the identity of a genomic clone encoding the enzyme selected from a genomic library of Z. mobilis DNA cloned into pUC9. The genomic fragment encoding the enzyme expressed high levels of pyruvate decarboxylase in Escherichia coli. Possible RNA polymerase and ribosome-binding sites have been identified in the 5'-untranslated region of the pyruvate decarboxylase gene.