Dr. Bray Links

Wednesday, January 18, 2017

Shikimate pathway & Glyphosate

The shikimate pathway (shikimic acid pathway) is a seven step metabolic route used by bacteria, fungi, algae, some protozoan parasites and plants for the biosynthesis of folates and aromatic amino acids (phenylalanine, tyrosine, and tryptophan). This pathway is not found in animals, which require these amino acids, hence the products of this pathway represent essential amino acids that must be obtained from bacteria or plants (or animals which eat bacteria or plants) in the animal's diet.


Glyphosate formulations and their use as antibiotics

The shikimate pathway is an ancient pathway that is involved in primary and secondary metabolism and is found in all prokaryotes, many lower eukaryotes, and plants, but not in mammals. In primary metabolism, the function of the pathway is to provide the precursors for the production of the aromatic amino acids and para-aminobenzoic acid. The shikimate pathway includes the enzymes and metabolites formed by converting 3-Deoxy-D-arabino-heptulosonic 3-phosphate (DAHP) to chorismic acid, the trifurication point for the three pathways leading to the production of tryptophane, tyrosine, and phenylalanine.

The importance of the shikimate pathway to cell viability is illustrated by experiments that result in the disruption of enzyme function. In plants, the shikimate pathway enzyme, EPSP synthase, has been targeted by a chemical inhibitor strategy that has resulted in the commercially successful, broad range, post-emergent herbicide called glyphosate. Glyphosate inhibits the shikimic acid pathway, which leads to the biosynthesis of aromatic compounds including amino acids, plant hormones, and vitamins. Specifically, glyphosate inhibits the conversion of phosphoenolpyruvic acid (PEP) and 3-phosphoshikimic acid to 5-enolpyruvyl-3-phosphoshikimic acid by binding to the enzyme 5-enolpyruvyishikimate-3-phosphate synthase (hereinafter referred to as EPSP synthase or EPSPS).


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