The phylogeny of the aromatic amino acid hydroxylases revisited by characterizing phenylalanine hydroxylase from Dictyostelium discoideum.
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 (DH4) than with tetrahydrobiopterin (BH4) as cofactor. DH4 is an abundant tetrahydropterin in D. discoideum while BH4 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.
Department of Biomedicine, University of Bergen, Jonas Lies vei 91, N-5009 Bergen, Norway.
Jessica
J
Siltberg-Liberles
Ida Helene
IH
Steen
Randi M
RM
Svebak
Aurora
A
Martinez
D000495:Allosteric Site; D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D003001:Cloning, Molecular; D004023:Dictyostelium / Q000201:enzymology*; D007700:Kinetics; D006899:Mixed Function Oxygenases / Q000378:metabolism*; D008968:Molecular Conformation; D008969:Molecular Sequence Data; D010651:Phenylalanine Hydroxylase / Q000378:metabolism*; D010802:Phylogeny; D011622:Pterins / Q000737:chemistry; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
D000596:Amino Acids; D011622:Pterins; C011552:tetrahydropterin; D006899:Mixed Function Oxygenases; D010651:Phenylalanine Hydroxylase