The cp4 epsps gene was isolated from the CP4 strain of the common
soil bacterium Agrobacterium tumefaciens. The enzyme
encoded by the sequence is a version of EPSPS that is highly
tolerant to inhibition by glyphosate and therefore leads to
increased tolerance to glyphosate-containing herbicides. The
following reaction is catalyzed by EPSPS:
3-phosphoshikimate + phosphoenolpyruvate =
5-O-(1-carboxyvinyl)-3-phosphoshikimate + phosphate
Glyphosate specifically binds to and inactivates the enzyme EPSPS,
which is part of an important plant biochemical pathway called the
shikimate pathway. The shikimate pathway is involved in the
biosynthesis of the aromatic amino acids tyrosine, phenylalanine
and tryptophan, as well as other aromatic compounds. When plants
are treated with glyphosate herbicides they cannot produce the
aromatic amino acids that are essential to their survival and,
therefore, die.
LMOs containing the glyphosate-tolerant epsps gene allow
farmers to use glyphosate-containing herbicides for weed control,
which will kill the weeds but not the LMO.
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