Disease relevance of Pah

• Reuber H4 hepatoma cells were also analyzed for phenylalanine hydroxylase mRNA [1].
• Classical phenylketonuria, an inborn error in metabolism, is caused by a deficiency of the hepatic enzyme phenylalanine hydroxylase [2].
• DCoH, the dimerization cofactor of hepatocyte nuclear factor-1, stimulates gene expression by associating with specific DNA binding proteins and also catalyzes the dehydration of the biopterin cofactor of phenylalanine hydroxylase [3].
• Epigenetic activation of phenylalanine hydroxylase in mouse erythroleukemia cells by the cytoplast of rat hepatoma cells [4].
• The over-expression of C. violaceum PAH in Escherichia coli will facilitate the analysis of the enzyme mechanism by various spectroscopic methods [5].

Psychiatry related information on Pah

• Hyperphenylalaninemia, which can cause neurological disorders and mental retardation, results from a mutation in phenylalanine hydroxylase or an enzyme required for biosynthesis or regeneration of its cofactor, tetrahydrobiopterin [6].

High impact information on Pah

• Phenylketonuria (PKU) is an autosomal recessive human genetic disorder caused by a deficiency of hepatic phenylalanine hydroxylase (PAH, phenylalanine 4-monooxygenase, EC 1.14.16.1) [7].
• To define the molecular basis of PKU, we characterized twelve restriction fragment-length polymorphism (RFLP) haplotypes of the PAH locus in the northern European population and observed that 90% of the PKU alleles in this population are confined to four common RFLP haplotypes [7].
• We have recently reported a splicing mutation in the PAH gene that is associated with RFLP haplotype 3 which is present at about 40% of mutant alleles [7].
• This defect is caused by a C-to-T transition in exon 12 resulting in an amino-acid substitution (Arg to Trp) at residue 408 of PAH [7].
• Direct hybridization analysis of the point mutation using a specific oligonucleotide probe demonstrated that this mutation is also in linkage disequilibrium with RFLP haplotype 2 alleles that make up about 20% of mutant PAH genes [7].

Chemical compound and disease context of Pah

• Mutant hepatoma cells which express very little phenylalanine hydroxylase contained less than 5% of the parental mRNA, but the gene still responded to hydrocortisone [1].
• Friend mouse erythroleukemia cells do not synthesize detectable levels of phenylalanine hydroxylase [phenylalanine 4-monooxygenase; L-phenylalanine, tetrahydropteridine:oxygen oxidoreductase (4-hydroxylating), EC 1.14.16.1] and hence are unable to grow in medium totally lacking tyrosine [4].
• The mechanism by which p-chlorophenylalanine specifically reduces phenylalanine hydroxylase activity in rat liver in vivo and in Reuber H4 hepatoma cells in culture has been investigated [8].
• To measure protein turnover in the Reuber hepatoma H4 cell line, cultures were labeled with [3H]leucine for specified periods after which phenylalanine hydroxylase was isolated and its leucine specific radioactivity determined [9].
• The complete amino acid sequence (296 amino acids) of Chromobacterium violaceum phenylalanine hydroxylase (PAH) was determined by nucleotide analysis of a DNA clone isolated using both a synthetic oligonucleotide probe based on the NH2-terminal amino acid sequence and an antibody against this enzyme [5].

Biological context of Pah

• Structural basis of autoregulation of phenylalanine hydroxylase [10].
• Screening of a rat liver cDNA expression library constructed in the vector lambda gt11 with an affinity purified antiserum to rat phenylalanine hydroxylase has resulted in the isolation of two clones which contain the complete coding region (1362 base pairs) of phenylalanine hydroxylase and the entire 3'-untranslated region (562 base pairs) [1].
• Purified rat liver phenylalanine hydroxylase was subjected to cyanogen bromide treatment, and the resulting fragments were used for N-terminal amino acid sequence analysis [2].
• A perfect match of 17 amino acid residues was found between the two sequences following a unique methionine codon present in the nucleotide sequence, thereby providing unambiguous evidence for the identity of the rat liver phenylalanine hydroxylase cDNA clones [2].
• Amino acid sequence at the phosphorylated site of rat liver phenylalanine hydroxylase and phosphorylation of a corresponding synthetic peptide [11].

Anatomical context of Pah

• Polysome immunoprecipitation of phenylalanine hydroxylase mRNA from rat liver and cloning of its cDNA [12].
• A full-length cDNA for tryptophan hydroxylase was cloned from rabbit pineal body by screening an expression library with antibody against rat phenylalanine hydroxylase, which crossreacts with rabbit tryptophan hydroxylase [13].
• Rat liver phenylalanine hydroxylase was expressed in both Escherichia coli and the Spodoptera frugiperda insect cell line, Sf9 [14].
• The rate of release of deuterons into the body water from 2,3,4,5,6-pentadeutero-L-phenylalanine has been shown to be a valid measure of the activity of the phenylalanine hydroxylase system in vivo [15].
• Immunoprecipitation of the phenylalanine hydroxylase formed by translation of rat liver RNA in a rabbit reticulocyte cell-free protein synthesis system was used to examine the origin of the molecular weight heterogeneity of the enzyme [16].

Associations of Pah with chemical compounds

• Phenylalanine hydroxylase converts phenylalanine to tyrosine, a rate-limiting step in phenylalanine catabolism and protein and neurotransmitter biosynthesis [10].
• Guanosine triphosphate (GTP) cyclohydrolase I, the rate-limiting enzyme in the biosynthesis of tetrahydrobiopterin (BH4), is subject to feedback inhibition by BH4, a cofactor for phenylalanine hydroxylase [17].
• alpha-Methylphenylalanine reduces the phenylalanine hydroxylase activity of rat liver by 75 percent [18].
• Evidence from cultures of REB15 cells, a strain derived by cloning H4 cells in tyrosine-free medium, suggested that the staining variability of H4 cells could reflect a variability in phenylalanine hydroxylase content [19].
• Hydrocortisone-treated H4 cells and REB15 cultures contain increased amounts of phenylalanine hydroxylase; and all cells in the culture appear to be induced by the hormone [19].

Regulatory relationships of Pah

• This phenomenon is a consequence of a decrease in the glucagon-stimulated phosphorylation of phenylalanine hydroxylase from liver cells incubated in the presence of insulin [20].

Other interactions of Pah

• The identification of putative cDNA clones coding for rat liver phenylalanine hydroxylase by hybrid-selected translation has previously been reported [Robson, K. J., Chandra, T., MacGillivray, R. T. A., & Woo, S. L. C. (1982) Proc. Natl. Acad. Sci. U.S.A. 79, 4701-4705] [2].
• The role of a polypeptide loop in tyrosine hydroxylase (TyrH) whose homolog in phenylalanine hydroxylase (PheH) takes on a different conformation when substrates are bound has been studied using site-directed mutagenesis [21].
• On the other hand, using catalase-supplemented assays, others have found that newborn rats have nearly adult levels of phenylalanine hydroxylase activity [22].
• The protective effect of glutathione peroxidase on phenylalanine hydroxylase suggests that the developmental time course found by McGee et al. may represent the slow developmental time course previously found for glutathione peroxidase [22].
• We also showed that the C2 phenotype included post-transcriptional effects for other genes: transcription of phenylalanine hydroxylase and phosphoenolpyruvate carboxykinase mRNA sequences continue in C2 at rates equivalent to FAO but these C2 cells have no mRNA for these proteins while FAO does [23].

Analytical, diagnostic and therapeutic context of Pah

• Sequence analysis of the rat phenylalanine hydroxylase gene promoter [24].
• The identity of the nuclear and cytoplasmic proteins is demonstrated by size, immunoblotting, stimulation of phenylalanine hydroxylase, and dehydratase activity [25].
• Cybrid clones expressed phenylalanine hydroxylase enzyme, which was of mouse type as determined by immunotitration and isoelectric focusing [4].
• Activation of rat liver phenylalanine hydroxylase by limited proteolysis catalyzed by chymotrypsin was investigated with the use of sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high pressure gel filtration [26].
• The circular dichroism spectra of the phenylalanine hydroxylase catalytic core suggested that it contains around 50% alpha-helix [27].

References