The phylogeny of the aromatic amino acid hydroxylases revisited by characterizing phenylalanine hydroxylase from Dictyostelium discoideum

• Published in: Gene Vol. 427; no. 1; pp. 86 - 92
• Main Authors: Siltberg-Liberles, Jessica, Steen, Ida Helene, Svebak, Randi M., Martinez, Aurora
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 31-12-2008
• Subjects: Allosteric Site; allosterism; Amino Acid Sequence; Amino Acids - metabolism; Amoeba; Animals; Cloning, Molecular; Dictyostelium - enzymology; Dictyostelium discoideum; genome duplications; Kinetics; Metazoa; Mixed Function Oxygenases - metabolism; Molecular Conformation; Molecular Sequence Data; phenylalanine catabolism; Phenylalanine Hydroxylase - metabolism; phylogenetic tree; Phylogeny; positive cooperativity; Pterins - chemistry; Sequence Homology, Amino Acid; Substrate Specificity; genome duplications; phylogenetic tree; BH 4; DTT; DH 4; DictyoPAH; MH 4; positive cooperativity; TPH; allosterism; TH; FH 4; AAAH; phenylalanine catabolism; hPAH
• ISSN: 0378-1119; 1879-0038
• DOI: 10.1016/j.gene.2008.09.005

The social amoeba
Dictyostelium discoideum contains only one aromatic amino acid hydroxylase (
AAAH) gene compared to at least three in metazoans. As shown in this work this gene codes for a phenylalanine hydroxylase (
DictyoPAH) and phylogenetic analysis places this enzyme close to the precursor AAAHs, aiding to define the evolutionary history of the AAAH family.
DictyoPAH shows significant similarities to other eukaryote PAH, but it exhibits higher activity with tetrahydrodictyopterin (DH
4) than with tetrahydrobiopterin (BH
4) as cofactor. DH
4 is an abundant tetrahydropterin in
D. discoideum while BH
4 is the natural cofactor of the AAAHs in mammals
. Moreover,
DictyoPAH is devoid of the characteristic regulatory mechanisms of mammalian PAH such as positive cooperativity for L-Phe and activation by preincubation with the substrate. Analysis of the few active site substitutions between
DictyoPAH and mammalian PAH, including mutant expression analysis, reveals potential structural determinants for allosteric regulation.