Sandbox Reserved 642: Difference between revisions
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== '''Structure''' == | == '''Structure''' == | ||
<Structure load='2PAH_tetramer3.pdb' size='500' frame='true' align='right' caption='This is a model of the pheylalanine hydroxylase dimer as found in humans. The green ball in within each subunit represents the iron ion in the catalytic domains.' scene='Insert optional scene name here' /> | <Structure load='2PAH_tetramer3.pdb' size='500' frame='true' align='right' caption='This is a model of the pheylalanine hydroxylase dimer as found in humans. The green ball in within each subunit represents the iron ion in the catalytic domains.' scene='Insert optional scene name here' /> | ||
PheOH can exist as a dimer or tetramer with identical subunits. Each subunit is organized to have a regulatory, catalytic and tetramerization domain. The native form of human PheOH has an estimated secondary structure composed 48% alpha-helices, 28% extended structures, 12% beta-turns, and 12% non-structured conformations. The more structured elements are usually concentrated in the catalytic C-terminal domain of the protein, while the more flexible and unstructured elements are grouped in the regulatory N-terminal domain.<ref>[www.ncbi.nlm.nih.gov/pubmed/9490012]</ref> The active site of PheOH can be found in the center of the catalytic domain and is characterized by a 13 Angrstrums deep and 10 Angstrums wide hydrophobic pocket. Lining the active site are 3 glutamates, 2 histadines and 1 tyrosine residues. The center of each catalytic domain consists of an iron ion which is vital to the enzyme activity and binds to histadine residues 285 and 290, 1 oxygen atom and glutamate 330. The PheOH model protein was generated via xray crystallography.<ref> Erlandsen,H. | PheOH can exist as a dimer or tetramer with identical subunits. Each subunit is organized to have a regulatory, catalytic and tetramerization domain. The native form of human PheOH has an estimated secondary structure composed 48% alpha-helices, 28% extended structures, 12% beta-turns, and 12% non-structured conformations. The more structured elements are usually concentrated in the catalytic C-terminal domain of the protein, while the more flexible and unstructured elements are grouped in the regulatory N-terminal domain.<ref>[www.ncbi.nlm.nih.gov/pubmed/9490012]</ref> The active site of PheOH can be found in the center of the catalytic domain and is characterized by a 13 Angrstrums deep and 10 Angstrums wide hydrophobic pocket. Lining the active site are 3 glutamates, 2 histadines and 1 tyrosine residues. The center of each catalytic domain consists of an iron ion which is vital to the enzyme activity and binds to histadine residues 285 and 290, 1 oxygen atom and glutamate 330. The PheOH model protein was generated via xray crystallography.<ref> Erlandsen,H. et al. Structural Studies on Phenylalanine Hydroxylase and Implications Toward Understanding and Treating Phenylketonuria [www.pkuworld.org/hom/docs/lierature/erlandsen_2003_p.pdf]</ref> | ||
== '''Mechanism''' == | == '''Mechanism''' == | ||
Although the exact mechanism of phenylalanine degradation is still not fully understood, the main reaction requires the addition of an hydroxyl group to the benzene ring of the phenylalanine residue. In order for this process to occur, the cofactor tetrahydrobiopterin(BH4) loses two hydrogen atoms to become dihydrobiopterin. BH4 acts as a reductant by reducing one of the diatomic oxygens while the other is added to the 6-membered ring. In order to stabilize the substrate- enzyme complex as this reaction occurs, an iron atom within the protein is necessary. It is within the active site that the hydrogen atom from phenylalanine is stripped off and replaced with a hydroxyl group. | Although the exact mechanism of phenylalanine degradation is still not fully understood, the main reaction requires the addition of an hydroxyl group to the benzene ring of the phenylalanine residue. In order for this process to occur, the cofactor tetrahydrobiopterin(BH4) loses two hydrogen atoms to become dihydrobiopterin. BH4 acts as a reductant by reducing one of the diatomic oxygens while the other is added to the 6-membered ring. In order to stabilize the substrate- enzyme complex as this reaction occurs, an iron atom within the protein is necessary. It is within the active site that the hydrogen atom from phenylalanine is stripped off and replaced with a hydroxyl group.<ref> [www.bio.davidson.edu/Courses/Molbio/MolStudents/spring2010/Piper/Protein.htm] </ref> | ||
[[Image:Phenylalanine_Hydroxylase_mechanism.jpg |thumb|450 px|center|Reaction catalyzed by PheOH]] | [[Image:Phenylalanine_Hydroxylase_mechanism.jpg |thumb|450 px|center|Reaction catalyzed by PheOH]] | ||
