Pseudomonas aeruginosa possesses homologues of mammalian phenylalanine hydroxylase and 4α-carbinolamine dehydratase/DCoH as part of a three-component gene cluster

Abstract

Pseudomonas aeruginosa possesses a multigene operon that includes phenylalanine hydroxylase (PhhA; phenylalanine4-monooxygenase, EC 1.14.16.1). phhA encodes PhhA (Mr = 30,288), phhB (Mr = 13,333) encodes a homologue of mammalian 4α-carbinolamine dehydratase/homeodomain protein transregulator, and phhC encodes an aromatic aminotransferase (Mr = 43,237). The reading frames specifying phhB and phhC overlap by 2 bases. The P. aeruginosa PhhA appears to contain iron and is pterin dependent. Unlike the multimeric mammalian hydroxylase, the native P. aeruginosa enzyme is a monomer. The P. aeruginosa PhhA is homologous with mammalian PhhA, tryptophan hydroxylase, and tyrosine hydroxylase. Expression of PhhA from its native promoter required phhB. This may suggest a positive regulatory role for phhB, consistent with the dual catalytic and regulatory roles of the corresponding mammalian homologue.