Glufosinate tolerant biotech crops utilize the deactivation mechanism, but rather than detoxifying the molecule, they alter its binding ability. The active ingredient of the herbicide glufosinate is phosphinothricine, which binds to the enzyme (glutamine synthase) that normally joins glutamate and ammonia to produce glutamine, an amino acid. By competing with glutamate for the enzyme’s active site, phosphinothricine harms plants through the accumulation of ammonia. Soil bacteria contain an enzyme, known as phosphinothricine acetyltransferase, or PAT, that adds an acetyl group to phosphinothricine. Biotech crops that contain a gene encoding the microbial PAT enzyme are capable of deactivating phosphinothricine via acetylation, which prevents it from binding with glutamine synthase.
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