The TyrA family includes enzymes with four specificities for the cyclohexadiencyl substrate. PapC participates in antibiotic synthesis and utilizes the 4-amino derivative of prephenate (PPA) as substrate. It can be recognized by its lack of an otherwise invariant residue that interacts with the 4-hydroxy substituent of the cyclohexadienyl substrate in the other three classes. The remaining three classes are alternative dehydrogenase reactions of TYR biosynthesis. TyrAa and TyrAp are specific for AGN and PPA, respectively. TyrAc enzymes have broad specificity and can recognize both AGN and PPA to various extents. A distinct variation of the TyrAc class, denoted as TyrAc_Δ, possesses deletion indels within the catalytic core region. Members of the known substrate-specificity types do not separate into cohesive phylogenetic subgroups, and no obvious discriminating motifs have been found.

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^a Abbreviations in the upper-table box indicate the specificities for the cyclohexadienyl substrate. Abbreviations in the lower-table box indicate specificities for both cyclohexadienyl (right subscripts) and pyridine nucleotide substrates (left subscripts). Combinations not shown can be deduced from the examples given, e.g., a TyrA homolog specific for prephenate and NAD⁺ would be designated _NADTyrA_p.

^b The abbreviations CDH, PDH, and ADH (shown parenthetically) have been used frequently in the literature.