Shikimate pathway

Route: Phosphoenolpyruvate + Erythrose 4-phosphate → 3-Deoxy-D-arabino-heptulosonate 7-phosphate → 3-Dehydroquinate → 3-Dehydroshikimate → Shikimate → Shikimate 3-phosphate + Phosphoenolpyruvate → 5-Enolpyruvylshikimate 3-phosphate → Chorismate

This is the route in bacteria, plants and fungi. Humans have none of these enzymes, which is why phenylalanine and tryptophan are essential amino acids for us. The first enzyme joins phosphoenolpyruvate (from glycolysis) to erythrose 4-phosphate (from the pentose phosphate pathway). The second turns the open chain into a six-membered ring, and the enzyme needs bound NAD⁺ to work. A dehydration puts in the first double bond, and NADPH reduces the keto group to give shikimate. Shikimate kinase adds a phosphate, and EPSP synthase attaches a second phosphoenolpyruvate unit to the ring. Chorismate synthase removes the first phosphate with reduced flavin (FMN) as a helper, which puts a second double bond into the ring and gives chorismate. Glyphosate, the herbicide, is an uncompetitive inhibitor of EPSP synthase and binds the enzyme together with shikimate 3-phosphate.

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Steps

Enzyme names and EC numbers are those used on the interactive board. Checked against sources: see the claim table in the repository (tools/pathway_data/checks).