Glufosinate is a racemic mixture of D- and L-phosphinothricin. L-phosphinothricin is a naturally-occurring bacterial amino acid that irreversibly inhibits glutamine synthetase (GS), resulting in death in green plants. The ammonium salt of glufosinate is widely known as phosphinothricin, or PPT, and used as the active ingredient in broad spectrum herbicides. Phosphinothricin acetyltransferase, encoded by the bar gene, converts PPT to a GS-inactive form. As a result, the bar gene is used as a selectable marker for genetic engineering in plants. As it confers resistance to the herbicide glufosinate rather than to an antibiotic, the bar gene may be preferred for selection of components for biological therapies, such as vaccines.
