The biosynthesis of all three aromatic amino acids (tryptophan, tyrosine and phenylalanine) begins with the metabolic intermediate chorismate. The biosynthesis of chorismate occurs only in plants and bacterial, not in animals. The first step in the pathway involves phosphoenolpyruvate (PEP) from glycolysis and erythrose-4-phosphate from the pentose phosphate pathway. These two precursors are condensed and then cyclized to form 3-dehydroquinate, followed by removal of a water and a reduction step to produce shikimate. Shikimate is phosphorylated, a pyruvate group from PEP added, and a phosphate removed to produce the pathway product chorismate. Shikimate and chorismate are also biosynthetic precursors in other microbial pathways.
Contributor: Glenn Croston, PhD.
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