Oil bodies of transgenicBrassica napus as a source of immobilized β-glucuronidase

The process of immobilizing enzymes is a major cost factor in the utilization of heterogeneous catalysts on an industrial scale. We have developed a new strategy, based on plant genetic manipulation, for the production of foreign peptides associated with the oil body in plant seeds. Seeds of transgenic rapeseed can be produced on a large scale at relatively low cost. Furthermore, oil bodies are readily isolated from seeds by floatation centrifugation. In this paper, we describe some physical and operational properties of an oil body—fusion protein complex and its suitability as a heterogeneous catalyst. Oil bodies from rapeseed, corn, and flax aggregate at pH 5, which facilitates their recovery by floatation. Oil bodies from transgenic rapeseed, carrying the reporter gene β-glucuronidase or the pharmaceutical peptide, hirudin, also aggregate in the same range. This aggregation is reversible. Oil bodies are resistant to a wide range of pH, with some lysis occurring (<10%) at the extremes. They are resistant to shearing forces, such as stirring. The thermal and pH stabilities, as well as the catalytic activity of β-glucuronidase expressed on the oil body surface, are comparable to those of free β-glucuronidase enzyme.