Large-scale production of a therapeutic protein in transgenic tobacco plants: effect of subcellular targeting on quality of a recombinant dog gastriclipase

A recombinant dog gastric lipase with therapeutic potential for the treatme nt of exocrine pancreatic insufficiency was expressed in transgenic tobacco plants. We targeted the protein using two different signal sequences for e ither vacuolar retention or secretion. In both cases, an active glycosylate d recombinant protein was obtained. The recombinant enzymes and the native enzyme displayed similar properties including acid resistance and acidic op timum pH. The proteolytic maturation and the specific activity of the recom binant proteins, however, were found to be dependent on subcellular compart mentalization. Expression levels of recombinant dog gastric lipase were abo ut 5% and 7% of acid extractable plant proteins for vacuolar retention and secretion respectively. This expression system already has allowed the prod uction of tens of grams of purified lipase through open-field culture of tr ansgenic tobacco plants.