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CABI Book Chapter

Amino acids in higher plants.

Book cover for Amino acids in higher plants.

Description

This book, divided into 5 parts, deals with topics on amino acids in higher plants. Part I (enzymes and metabolism) contains 16 chapters pursuing the theme of amino acid metabolism through the driving actions of the principal enzymes, emphasizing recent advances particularly with reference to localization, biophysical characterization and regulation. Part II (dynamics) includes two chapters design...

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Chapter 24 (Page no: 461)

Glyphosate: the fate and toxicology of a herbicidal amino acid derivative.

Glyphosate was first registered in the USA in 1974 for non-crop and industrial use as a herbicide. With the advent of glyphosate-tolerant crops and the adoption of minimum and no-till practices, it has become one the world's foremost herbicides. Glyphosate inhibits a key step in the shikimate acid pathway and thereby the synthesis of the aromatic amino acids tyrosine, phenylalanine and tryptophan in plants. This is achieved by glyphosate binding to the enzyme 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). As the shikimate pathway is not present in the animal kingdom, animals cannot synthesize these three aromatic amino acids, which are therefore considered essential for humans and must be acquired via the diet. Following foliar application, glyphosate penetrates the cuticle and is rapidly absorbed and translocated throughout the plant. Aminomethylphosphonic acid (AMPA) is the predominant metabolite within plants. Environmental degradation of glyphosate occurs primarily via microbial degradation, which also produces AMPA on the pathway to full mineralization. In vitro metabolic studies in mammals have demonstrated that nearly all glyphosate is excreted unchanged, and what little AMPA is formed is most likely attributable to the metabolism of gastrointestinal microflora. Glyphosate has undergone extensive toxicology testing over the last 40 years, with at least six separate toxicology data sets generated by different registering companies across the globe. These data are remarkably consistent in demonstrating an absence of concern for developmental and reproductive toxicity, and no carcinogenicity, no genotoxicity, no endocrine disruption potential, no neurotoxicity and no immunotoxicity. AMPA has been shown to be of equal or lesser toxicity to the parent compound. In contrast, published literature and the Internet are bestrewn with allegations of adverse toxic effects attributable to glyphosate, but these are largely data collected from high-dosed in vitro test systems, from studies using inappropriate routes of exposure or by unvalidated test methods.

Other chapters from this book

Chapter: 1 (Page no: 1) Glutamate dehydrogenase. Author(s): Osuji, G. O. Madu, W. C.
Chapter: 2 (Page no: 30) Alanine aminotransferase: amino acid metabolism in higher plants. Author(s): Raychaudhuri, A.
Chapter: 3 (Page no: 57) Aspartate aminotransferase. Author(s): Leasure, C. D. He, Z. H.
Chapter: 4 (Page no: 68) Tyrosine aminotransferase. Author(s): Hudson, A. O.
Chapter: 5 (Page no: 82) An insight into the role and regulation of glutamine synthetase in plants. Author(s): Sengupta-Gopalan, C. Ortega, J. L.
Chapter: 6 (Page no: 100) Asparagine synthetase. Author(s): Duff, S. M. G.
Chapter: 7 (Page no: 129) Glutamate decarboxylase. Author(s): Molina-Rueda, J. J. Garrido-Aranda, A. Gallardo, F.
Chapter: 8 (Page no: 142) L-arginine-dependent nitric oxide synthase activity. Author(s): Corpas, F. J. Río, L. A. del Palma, J. M. Barroso, J. B.
Chapter: 9 (Page no: 156) Ornithine: at the crossroads of multiple paths to amino acids and polyamines. Author(s): Majumdar, R. Minocha, R. Minocha, S. C.
Chapter: 10 (Page no: 177) Polyamines in plants: biosynthesis from arginine, and metabolic, physiological and stress-response roles. Author(s): Mattoo, A. K. Fatima, T. Upadhyay, R. K. Handa, A. K.
Chapter: 11 (Page no: 195) Serine acetyltransferase. Author(s): Watanabe, M. Hubberten, H. M. Saito, K. Hoefgen, R.
Chapter: 12 (Page no: 219) Cysteine homeostasis. Author(s): García, I. Romero, L. C. Gotor, C.
Chapter: 13 (Page no: 234) Lysine metabolism. Author(s): Medici, L. O. Nazareno, A. C. Gaziola, S. A. Schmidt, D. Azevedo, R. A.
Chapter: 14 (Page no: 251) Histidine. Author(s): Ingle, R. A.
Chapter: 15 (Page no: 262) Amino acid synthesis under abiotic stress. Author(s): Planchet, E. Limami, A. M.
Chapter: 16 (Page no: 277) The central role of glutamate and aspartate in the post-translational control of respiration and nitrogen assimilation in plant cells. Author(s): O'Leary, B. Plaxton, W. C.
Chapter: 17 (Page no: 298) Amino acid export in plants. Author(s): Price, M. B. Okumoto, S.
Chapter: 18 (Page no: 315) Uptake, transport and redistribution of amino nitrogen in woody plants. Author(s): Pfautsch, S. Bell, T. L. Gessler, A.
Chapter: 19 (Page no: 340) Auxin biosynthesis. Author(s): Chandler, J. W.
Chapter: 20 (Page no: 362) Involvement of tryptophan-pathway-derived secondary metabolism in the defence responses of grasses. Author(s): Ishihara, A. Matsukawa, T. Nomura, T. Sue, M. Oikawa, A. Okazaki, Y. Tebayashi, S.
Chapter: 21 (Page no: 390) Melatonin: synthesis from tryptophan and its role in higher plant. Author(s): Arnao, M. B. Hernández-Ruiz, J.
Chapter: 22 (Page no: 436) Glucosinolate biosynthesis from amino acids. Author(s): Stotz, H. U. Brown, P. D. Tokuhisa, J.
Chapter: 23 (Page no: 448) Natural toxins that affect plant amino acid metabolism. Author(s): Duke, S. O. Dayan, F. E.
Chapter: 25 (Page no: 481) Amino acid analysis of plant products. Author(s): Rutherfurd, S. M.
Chapter: 26 (Page no: 497) Metabolic amino acid availability in foods of plant origin: implications for human and livestock nutrition. Author(s): Levesque, C. L.
Chapter: 27 (Page no: 507) Toxicology of non-protein amino acids. Author(s): D'Mello, J. P. F.
Chapter: 28 (Page no: 538) Delivering innovative solutions and paradigms for a changing environment. Author(s): D'Mello, J. P. F.

Chapter details

  • Author Affiliation
  • Regulatory Product Safety Center, Monsanto, 800 North Lindberg Boulevard, St Louis, MO 63167, USA.
  • Year of Publication
  • 2015
  • ISBN
  • 9781780642635
  • Record Number
  • 20153121434