Crop biomanufacturing of enzyme gets underway in US
of a transgenic tobacco crop that will be used to produce an enzyme
with potential as an active pharmaceutical ingredient and as a
catalyst for the manufacture of industrial chemicals.
The field trial, carried out in collaboration with the Kentucky Tobacco Research and Development Centre (KTRDC) in Lexington, US, will involve transgenic plants with genetically engineered chloroplasts containing a phenylalanine ammonia lyase (PAL) gene from Arabidopsis thaliana.
An overexpression of the PAL gene in tobacco chloroplasts aims at both pharmaceutical and industrial applications: the purified enzyme can serve as a drug for the treatment of the inherited disease phenylketonuria (PKU). The enzyme also serves as a biocatalyst for industrial biochemical synthesis, particularly chiral compounds. Futhermore, expression of PAL in the plants will lead to the accumulation of metabolites from the phenylpropane pathway that are also of commercial value, according to Icon.
Making pharmaceuticals in crop plants such as tobacco is an attractive proposition because they are inexpensive to grow, and could produce vast quantities of drugs or vaccines at low cost, potentially making it possible to make drugs that were not economically feasible before. But moves in this area have been met with dismay by environmentalist groups, alarmed that the GM traits could find their way into the food chain.
ICON said that biosafety aspects of the field trial, which has been granted a release permit by the US Government's Animal and Plant Health Inspection Service, have been 'carefully considered'.
The firm maintains that chloroplast-located transgenes generally do not spread into the environment via pollen flow. Moreover, the genetically engineered plants do not contain antibiotic resistance genes, according to the company, since they were created using ICON's proprietary resistance marker removal technology.
"The tobacco plants do not contain any foreign genetic sequences except those required for PAL protein biosynthesis. Expression is achieved by extending an existing operon, thus additional promoter elements, which may lead to genetic instability, are not required," explained ICON's manager, Christian Eibl.
