Shikimate pathway

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

The shikimate pathway is a seven-step process that bacteria, archaea, fungi, algae, some protozoa, and plants use to make folates and the aromatic amino acids tyrosine, phenylalanine, and tryptophan. Animals, including humans, don’t have this pathway.

Five key enzymes drive the steps: 3-dehydroquinate dehydratase, shikimate dehydrogenase, shikimate kinase, EPSP synthase, and chorismate synthase.

In bacteria and plants, the pathway starts with two ingredients, phosphoenol pyruvate (PEP) and erythrose-4-phosphate, which are turned into DAHP and then into 3-dehydroquinate. In archaea, a different starting reaction builds the same end product, 3-dehydroquinate.

All routes end with chorismate, which is the building block for making the three aromatic amino acids.

Key steps include:
- Shikimate kinase adds a phosphate to shikimate to form shikimate-3-phosphate.
- EPSP synthase combines shikimate-3-phosphate with PEP to make EPSP.
- Glyphosate (the herbicide Roundup) blocks EPSP synthase, shutting down the pathway.
- Chorismate synthase converts EPSP to chorismate; chorismate can be rearranged by chorismate mutase to prephenate, which is then turned into p-hydroxyphenylpyruvate and, with the help of glutamate, into tyrosine. Phenylalanine and tryptophan are made from related steps starting from prephenate.