<p style="text-align: justify;">Maize line NK603 was developed to allow the use of glyphosate containing herbicides as a weed control option for maize crops. The gene encoding a glyphosate tolerant form of the enzyme 5-enolpyruvlyshikimate-3-phosphate synthase (EPSPS) was isolated from the soil bacterium <i>Agrobacterium tumefaciens</i> strain CP4 and introduced into maize using recombinant DNA techniques. Glyphosate specifically binds to and inactivates EPSPS, which is involved in the biosynthesis of the aromatic amino acids tyrosine, phenylalanine and tryptophan. This enzyme is present in all plants, bacteria and fungi, but not in animals, which do not synthesize their own aromatic amino acids. Thus, EPSPS is normally present in food derived from plant and microbial sources.<br />
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For environmental release in the United States, another glyphosate tolerant maize line, GA21, was designated as the antecedent organism for NK603. Maize line NK603 and the antecedent organism GA21 were genetically engineered using the same transformation method and contain a functionally equivalent enzyme that makes the plants tolerant to the herbicide glyphosate.</p>
