Tyrosine, biosynthesis

Tetrahydrobiopterin is the reduced form of dihydrobiopterin, an electron carrier in tyrosine biosynthesis (Figure 21.18). Tyrosine is only aromatic amino acid made in animals. The reaction is catalyzed by phenylalanine hydroxylase. 

L-tyrosine biosynthesis in mung bean (Vigna radiata [L.] Wilczek). Plant Physiol. 64 727-734. 

Enz3nnology of JL-tyrosine biosynthesis in corn (Zea mays). Phytochemistry 20 1289-1292. 

L-Tyrosine biosynthesis starts with the condensation of phosphoenolpyruvate (PEP) and erythrose-4-phosphate (E4P), the intermediates of the glycolytic pathway and pentose phosphate pathway, respectively, which is catalyzed by 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase (DAHPS aroE/aroG/aroH). The resultant 3-deoxy-D-arabino-heptulosonate (DAHP) is converted into chorismate through the shikimate pathway with seven reactions. In plants, prephenate (PPA) is converted into L-arogenate by transamination whereas in E. coli, PPA is converted to p-hydroxyphenylpyruvate (HPP) by prephenate dehydrogenase, which is a bifunctional enzyme that behaves as chorismate mutase/prephenate... 

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