Tobacco Chloroplasts as Bioreactors for the Production of Recombinant Superoxide Dismutase in Plants, an Industrially Useful Enzyme

An inexpensive source of industrially useful enzymes is critical for their commercial production. We have produced an industrially valuable recombinant superoxide dismutase (SOD) in tobacco chloroplasts. A gene from Withania somnifera, encoding a highly stable Cu/Zn SOD, was cloned into a chloroplast transformation vector. It expressed the SOD in tobacco chloroplasts following transformation. The transplastomic plants accumulated the recombinant SOD at up to similar to 9% of the total soluble protein in leaves. The purified chloroplast-expressed recombinant SOD had an estimated specific activity of similar to 4600 U/mg. Like the native enzyme, purified recombinant enzyme, prepared from tobacco leaves, was highly stable at high temperatures and tolerated a wide pH range, SDS, ethanol and protease treatment. The results establish the potential of chloroplast transformation for commercial production of recombinant SOD in plants.