SUBCELLULAR LOCATION OF THE TETRAPYRROLE SYNTHESIS ENZYME PORPHOBILINOGEN DEAMINASE IN HIGHER-PLANTS - AN IMMUNOLOGICAL INVESTIGATION

A recombinant plasmid, pArab8, harbouring the cDNA encoding the mature form of the tetrapyrrole synthesis enzyme porphobilinogen deaminase ( EC 4.3.1.8; also known as hydroxymethylbilane synthase) from Arabidops is thaliana (L.) Heynh. has been constructed, and used to transform Es cherichia coli. The porphobilinogen deaminase protein from Arabidopsis was overexpressed in this strain, and purified to homogeneity (3000-f old) with a yield of 20%. Antibodies were raised against the purified plant enzyme, and used in Western blot analysis, immunoprecipitation o f enzyme activity and immune-gold electron microscopy. The results ind icate that the enzyme is confined to plastids in both leaves and roots . The implications of this finding for plant tetrapyrrole synthesis ar e discussed.