Herbicides, Roundup

All carbons are derived from either erythrose 4-phosphate (light purple) or phosphoenolpyruvate (pink). Note that the NAD+ required as a cofactor in step (3) is released unchanged it may be transiently reduced to NADH during the reaction, with formation of an oxidized reaction intermediate. Step (6) is competitively inhibited by glyphosate (COO—CH2—NH—CH2—PO ), the active ingredient in the widely used herbicide Roundup. The herbicide is relatively nontoxic to mammals, which lack this biosynthetic pathway. The chemical names quinate, shikimate, and chorismate are derived from the names of plants in which these intermediates have been found to accumulate. 

By late 1996, Monsanto had planned to divide itself into two entities Monsanto Life Sciences and a chemical entity (later given the name Solutia) (Reisch). This occurred within a year, during which Monsanto purchased a plant biotechnology company (Calgene) that held patents for improved fresh produce, cotton seeds, specialty industrial and edible oils (derived from seeds) and plant varieties (Anonymous, 1997). Based on analysis of 1995 sales, the life sciences products accounted for annual sales of S5.3 billion based on the major products of Round-up herbicide, Roundup-resistant soybeans, Bollguard insect-protected cotton, Nutrasweet sweetner, and prescription drugs for arthritis and insomnia. 

In recent years, agribusiness firms have developed pf empirically several compounds that inhibit essential steps in the biosynthesis of amino acids found in plants but missing in animals. One of these compounds, glyphosate, is a highly specific inhibitor of 5-enol pyruvyl-shikimate-3-phosphate synthase (an enzyme needed for aromatic amino acid biosynthesis). Glyphosate is the active ingredient in the widely used herbicide Roundup. 

The herbicide Roundup kills all natural plants it encounters. It began to be used in the 1990s in combination with genetically engineered crops that include a gene intended to make the crop (and only the crop) resistant to the herbicide. This combination of chemical and genetic technology has been an economic success but it has raised many concerns about potential problems in the future. 

The advantage for the farmer is that he needs only one product, instead of several different selective (and more expensive) herbicides. Roundup ready soybeans were launched in 1996 and today 50 percent of the soybean crop in the United States is derived from roundup ready seeds. Other glyphosate-resistant transgenic crops introduced by Monsanto are maize and oil seed rape. Competing companies also developed herbicide-resistant plants or plants genetically modified to be protected against certain pests, but none has achieved a commercial breakthrough, mainly because of political reasons. 

N-(Phosphonomethyl) glycine. This material, closely related chemically and probably biologically to Polaris, has been given the generic name of glyphosate. As the isopropylamine salt, it is the very potent herbicide Roundup which is especially active on grasses. It has been tested as the isopropylamine salt, as the acid, and in several other forms as a ripener on sugarcane and was found to be extremely active—in fact, much more active than Polaris itself. 

Williams GM, Kroes R, and Munro IC (2000) Safety evaluation and risk assessment of the herbicide Roundup and its active ingredient, glyphosate, for humans. Regulatory Toxicology and Pharmacology 31 117-165. 

Kemmer (1978) investigated the effect of the herbicide Roundup on stubble-field against Agropyron repens at application rates of 4-6-8 l/ha and found that the effect depends more on the time of application than on the dose. For optimal effect spraying must be done at least two weeks before ploughing. 

Best known as genes conveying new properties are the EPSPS gene from the plant Petunia hybrida, which codes for tolerance to the herbicide Roundup Ready [this is found in the Roundup Ready soybean (RRS)], and the cry genes from Bacillus... 

The major nitrile products produced in addition to acrylonitrile, HCN, and acetonitrile have significant commercial value in their own right. HCN is used mainly in the manufacture of methyl methacrylate. Methyl methacrylate is prepared by acid dehydration and methanol esterification of acetone cyanohydrin produced from the reaction of HCN and acetone. HCN is also a feedstock for the production of methionine, an important animal feed supplement, and is used to produce pesticides and herbicides. For example, HCN is utilized to manufacture disodium iminodiacetate, which is a key intermediate in the production of the widely used herbicide Roundup (Monsanto Co., St. Louis U.S.A.). It is also valuable as a feedstock for the production of adiponitrile by the hydrocyana-tion of butadiene. Adiponitrile is a feedstock for the manufacture of Nylon. In... 

This homogeneous catalytic conversion is novel and represents, in effect, an oxidative dealkylation of one carboxymethyl moiety, yielding the N-substituted glycine. The reaction is selective to the desired product PMG when carried out at the natural pH of the free acid substrate (approximately 1-2) and when carried out at substrate loadings less than 5% by weight. PMG is the active agent in the herbicide Roundup... 

Another issue is that repeated use of a same herbicide Roundup may enhance the development of a resistance against it among some plants including the weeds that are intended to be the target of Roundup. Indeed the so-called superweeds that are resistant to Roundup have already developed in some areas. This will necessitate an increased use of the herbicide and eventually may also require use of other herbicides. This will negate the original intention of this GM plant. 

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