Hirudin A Polypeptide - Hirudin is encoded by a synthetic gene, and is expressed in fusion with the oil body protein olesin which greatly facilitates the purification of hirudin. The seed tissue expressing hirudin fused with ole sin is extracted with water and the extract is centrifuged.

Oil bodies containing the olesin fusion protein float on the surface, and are easily separated from the rest of seed proteins. The hirudin is cleaved from olesin at a protease recognition site located at their junction. Thus hirudin provides a successful example of transgene expression in plants for the isolation of a polypeptide of interest at a commercial scale.