Chorismate mutase prephenic acid from

Both phenylalanine and tyrosine are derived from chorismic acid, which is itself derived from shikimic acid-3-phosphate through the shikimic acid pathway. In this sequence, chorismic acid is first transformed into prephenic acid by chorismate mutase. If prephenic acid is converted into phenylpyruvic acid by... 

In higher plants, phenylalanine seems to be formed in an alternative manner by formation of prephenate (26) and conversion of this intermediate into arogenic acid (32). Chorismate mutase occurs as two isozymes which have been purified to homogeneity from mung bean and sorghum. All chorismate mutase isozymes show allosteric activation by chorismate (Poulsen and Verpoorte, 1991). One chorismate mutase isozyme is inhibited by phenylalanine or tyrosine and activated by tryprophan, whereas the second is not affected by any of the aromatic amino acids. 

Chorismic acid is the key branch point intermediate in the biosynthesis of aromatic amino acids in microorganisms and plants (Scheme 1.1a) [1]. In the branch that leads to the production of tyrosine and phenylalanine, chorismate mutase (CM, chorismate-pyruvate mutase, EC 5.4.99.5) is a key enzyme that catalyzes the isomerization of chorismate to prephenate (Scheme 1.1b) with a rate enhancement of about lO -lO -fold. This reaction is one of few pericyclic processes in biology and provides a rare opportunity for understanding how Nature promotes such unusual transformations. The biological importance of the conversion from chorismate to prephenate and the synthetic value of the Claisen rearrangement have led to extensive experimental investigations [2-43]. 

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