Glyphosate is a 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS; EC 2.5.1.19) was first patented as an industrial detergent by Stauffer Chemical Company (Acs, 1997). The Chemical company Monsanto finally patented glyphosate as a non-selective herbicide in 1974. Initially, glyphosate use was low, mainly because it was non-selective and expensive. However, with the advent of genetically modified glyphosate resistant crops and the expiration of patents, glyphosate has become the most widely used herbicide in the world. In the United States, glyphosate has been the most commonly used pesticide since 2001, with over 81.6 million kg used in 2007 (Grube et al., 2011).
EPSPS is the penultimate enzyme in the aromatic amino acid pathway that ultimately produces tyrosine, tryptophan, and phenylalanine, and is fortunately absent in mammals (Haslam, 1993). Inhibition of EPSPS depletes these important amino acids in treated plants; Conversely, functional proteins cannot be made. Under normal application conditions, plant death is usually due to the depletion of important secondary plant metabolites, especially those associated with disease resistance. The EPSPS enzyme is localized in chloroplasts and converts shikimate 3-phosphate to enolpyruvate shikimate 3-phosphate (Amrhein et al., 1980). Introduction of glyphosate into the plant system causes shikimic acid to accumulate in the form of 3-phosphate shikimic acid, which is unstable. EPSPS is a monomeric enzyme consisting of two domains linked by protein chains. When Shikimate-3-phosphate binds to EPSPS, the two domains tighten together, trapping the substrate at the active site (Schonbrunn et al., 2001). Glyphosate then permanently occupies the binding site of the second substrate of EPSPS, phosphoenolpyruvate.
Glyphosate as a amphoteric ion is usually formulated as a salt. Three salts have been used: isopropylamine, trimethylammonium and potassium. Glyphosate has a variety of uses and is usually built around achieving selectivity through placement, timing or genetic modification. Another section of this encyclopedia covers this topic.
Glyphosate is usually sold as isopropylamine, potassium, ammonium or trimethyl sulfonate salts. Although glyphosate is not a low-use herbicide, its acute toxicity to mammals is lower than that of table salt. When sprayed on plants, it is easily absorbed and transferred to all parts of the plant. Generally do not detoxify or detoxify very slowly. It acts relatively slowly, giving the herbicide time to reach almost all tissues of the plant. In addition, it preferentially metastasizes to metabolic sinks such as meristem. As a result, affected plants are less likely to regenerate from the meristem.
