L-phenylalanine and L-tyrosine biosynthesis from chorismate

Branch of aromatic amino acid biosynthesis that converts chorismate to L-phenylalanine and L-tyrosine in bacteria, fungi and plants. Chorismate mutase rearranges chorismate to prephenate; this committed step is the main point of feedback control, typically inhibited by tyrosine (and in fungi and plants activated by tryptophan). Prephenate is then converted by one of two routes. In the prephenate route used by fungi and most bacteria, prephenate dehydratase gives phenylpyruvate and prephenate dehydrogenase gives 4-hydroxyphenylpyruvate, and aromatic aminotransferases convert these keto acids to phenylalanine and tyrosine. In the arogenate route that predominates in plants, prephenate aminotransferase first gives arogenate, which arogenate dehydratase and arogenate dehydrogenase convert to phenylalanine and tyrosine. In enteric bacteria chorismate mutase is fused to the dehydratase (P-protein) or the dehydrogenase (T-protein); in fungi and plants it is a separate allosteric enzyme. Synthesis of chorismate, the tryptophan branch and the hydroxylation of phenylalanine to tyrosine are outside this module.

NEW module (YeastPathways crosswalk, 2026-10) generalising PWY3O-4153 (phenylalanine) and PWY3O-4120 (tyrosine). COMPLETE-ARO-PWY-1 is the union of bacterial_shikimate_chorismate_biosynthesis, tryptophan_biosynthesis and this module, and is not modelled itself. The upstream shikimate module produces the chorismate consumed here. Structure: chorismate mutase, then a route variant set (prephenate route versus arogenate route), each route with a phenylalanine arm and a tyrosine arm. The shared terminal transamination of the prephenate route is a single part with an aminotransferase-family variant set. YeastCyc corrections: (1) HIS5 (histidinol-phosphate aminotransferase) is listed by YeastCyc for phenylalanine transamination (RXN-10814) but is not modelled. There is no yeast evidence that it acts as an aromatic aminotransferase in vivo: aro8 aro9 double mutants are Phe/Tyr auxotrophs (PMID:9491082). (2) TYR1 is assigned EC 1.3.1.13 (NADP+) by YeastCyc and typed GO:0004665 in the SGD GO-CAMs, but the purified enzyme favours NAD+ (PMID:30771296). The module uses GO:0008977 and EC 1.3.1.12, matching the PomBase model. (3) The YeastCyc phenylalanine:pyruvate and tyrosine:pyruvate reactions (EC 2.6.1.58) assigned to ARO9 reflect its catabolic and amino-acceptor role (it is induced by aromatic amino acids). The SGD GO-CAMs nonetheless type them with the 2-oxoglutarate term GO:0008793. ARO9 is kept as a secondary, redundant biosynthetic aminotransferase. No missing enzymes were found for S. cerevisiae. Compartment: all yeast and S. pombe activities are cytosolic, whereas in plants the arogenate route enzymes and chorismate mutase CM1 are plastidic; no compartment is asserted at module level. GO-CAM disagreements: the PomBase model places aro7 chorismate mutase part_of GO:0009423 chorismate biosynthesis rather than phenylalanine/tyrosine biosynthesis. The SGD models have no causal or input/output links. Scope exclusions: tyrosine formed by phenylalanine 4-hydroxylation (animals, some bacteria), the fungal Ehrlich catabolic pathway (ARO9, ARO10) and cyclohexadienyl dehydrogenases of some bacteria are not modelled. Plant ADTs with residual prephenate dehydratase activity (ADT1, ADT2) can also supply the prephenate route in plants (PMID:21388819). Some aminotransferases, such as S. cerevisiae ARO8, have broad specificity that includes alpha-aminoadipate (PMID:9491083).