The crystal structure of Cyclohexadienyl dehydratase precursor from Pseudomonas aeruginosa PA01. The secondary structure is displayed in the image, and the residue important for catalysis has been highlighted.
This enzyme belongs to the family of lyases, specifically the hydro-lyases, which cleave carbon-oxygen bonds. The systematic name of this enzyme class is L-arogenate hydro-lyase (decarboxylating; L-phenylalanine-forming). Other names in common use include:
arogenate dehydratase
L-arogenate hydro-lyase (decarboxylating)
cyclohexadienyl dehydratase
carbocyclohexadienyl dehydratase
pheC
ADT
Reaction
The carboxyl and hydroxide groups (shown in red) attached to the 2,5-cyclohexene ring are eliminated from L-arogenate, leaving as carbon dioxide and water. The 2,5-cyclohexene ring becomes a phenyl ring, and L-phenylalanine is formed.
Certain forms of ADT have been shown to exhibit some prephenate dehydratase (PDT) activity in addition to the standard ADT activity described above.[1] Known as cyclohexadienyl dehydratases or carbocyclohexadienyl dehydratases (listed above),[1] these forms of the enzyme catalyze the same type of reaction (a decarboxylation and a dehydration) on prephenate. The carboxyl and hydroxide groups (in red) attached to the 2,5-cyclohexene ring are removed, leaving phenylpyruvate.
Function
ADT catalyzes a reaction categorized by two major changes in the structure of the substrate, these being a decarboxylation and a dehydration; the enzyme removes a carboxyl group and a water molecule (respectively).[1] Both potential products of this reaction (L-arogenate and phenylpyruvate) occur at or near the end of the biosynthetic pathway. Total synthesis of L-arogenate has been reported.[3][4]
^Danishefsky S, Morris J, Clizbe LA (2002-05-01). "Total synthesis of pretyrosine (arogenate)". Journal of the American Chemical Society. 103 (6): 1602–1604. doi:10.1021/ja00396a070.
^Siehl DL, Conn EE (February 1988). "Kinetic and regulatory properties of arogenate dehydratase in seedlings of Sorghum bicolor (L.) Moench". Archives of Biochemistry and Biophysics. 260 (2): 822–9. doi:10.1016/0003-9861(88)90513-9. PMID3124763.
^Xia TH, Ahmad S, Zhao GS, Jensen RA (May 1991). "A single cyclohexadienyl dehydratase specifies the prephenate dehydratase and arogenate dehydratase components of one of two independent pathways to L-phenylalanine in Erwinia herbicola". Archives of Biochemistry and Biophysics. 286 (2): 461–5. doi:10.1016/0003-9861(91)90066-r. PMID1897969.