The liver enzyme phenylalanine hydroxylase is responsible for catabolism of excess phenylalanine in the diet. Deficiencies in levels of the enzyme result in the metabolic disorder phenylketonuria, a disease with devastating neurological consequences if untreated, demonstrating the physiological importance of the enzyme. Central to the proper function of phenylalanine hydroxylase is the regulation of the enzyme by its substrates, phenylalanine and tetrahydrobiopterin, and by phosphorylation. Both forms of regulation require the N-terminal ~117 residue regulatory domain. In the generally-accepted model for regulation, the resting form of the enzyme is inactive and allosteric binding of phenylalanine at a regulatory site converts the enzyme to an active form. Tetrahydrobiopterin stabilizes the inactive form, while phosphorylation potentiates the conversion to the active form. The goal of the research proposed here is to understand the structural and dynamic basis for the allosteric regulation. The proposed experiments will combine modern structural approaches (e.g., NMR and mass spectroscopy) with measurement of intrinsic rate constants for binding and catalysis in order to provide a more complete understanding of the allosteric regulation of phenylalanine hydroxylase.

Public Health Relevance

This is a proposal to study the regulation of the liver enzyme phenylalanine hydroxylase. An inherited deficiency in this enzyme unless the affected individual is placed on a restricted diet from birth. A better understanding of the regulation will improve our ability to develop better treatments for PKU.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Project (R01)
Project #
5R01GM098140-03
Application #
8470665
Study Section
Special Emphasis Panel (ZRG1-BCMB-B (03))
Program Officer
Anderson, Vernon
Project Start
2011-09-20
Project End
2015-05-31
Budget Start
2013-06-01
Budget End
2014-05-31
Support Year
3
Fiscal Year
2013
Total Cost
$271,223
Indirect Cost
$89,803
Name
University of Texas Health Science Center San Antonio
Department
Biochemistry
Type
Schools of Medicine
DUNS #
800772162
City
San Antonio
State
TX
Country
United States
Zip Code
78229
Zhang, Shengnan; Fitzpatrick, Paul F (2016) Identification of the Allosteric Site for Phenylalanine in Rat Phenylalanine Hydroxylase. J Biol Chem 291:7418-25
Meisburger, Steve P; Taylor, Alexander B; Khan, Crystal A et al. (2016) Domain Movements upon Activation of Phenylalanine Hydroxylase Characterized by Crystallography and Chromatography-Coupled Small-Angle X-ray Scattering. J Am Chem Soc 138:6506-16
Zhang, Shengnan; Hinck, Cynthia S; Fitzpatrick, Paul F (2016) The regulatory domain of human tryptophan hydroxylase 1 forms a stable dimer. Biochem Biophys Res Commun 476:457-61
Fitzpatrick, Paul F (2015) Structural insights into the regulation of aromatic amino acid hydroxylation. Curr Opin Struct Biol 35:1-6
Zhang, Shengnan; Hinck, Andrew P; Fitzpatrick, Paul F (2015) The Amino Acid Specificity for Activation of Phenylalanine Hydroxylase Matches the Specificity for Stabilization of Regulatory Domain Dimers. Biochemistry 54:5167-74
Roberts, Kenneth M; Khan, Crystal A; Hinck, Cynthia S et al. (2014) Activation of phenylalanine hydroxylase by phenylalanine does not require binding in the active site. Biochemistry 53:7846-53
Zhang, Shengnan; Roberts, Kenneth M; Fitzpatrick, Paul F (2014) Phenylalanine binding is linked to dimerization of the regulatory domain of phenylalanine hydroxylase. Biochemistry 53:6625-7
Zhang, Shengnan; Huang, Tao; Ilangovan, Udayar et al. (2014) The solution structure of the regulatory domain of tyrosine hydroxylase. J Mol Biol 426:1483-97
Roberts, Kenneth M; Pavon, Jorge Alex; Fitzpatrick, Paul F (2013) Kinetic mechanism of phenylalanine hydroxylase: intrinsic binding and rate constants from single-turnover experiments. Biochemistry 52:1062-73
Li, Jun; Fitzpatrick, Paul F (2013) Regulation of phenylalanine hydroxylase: conformational changes upon phosphorylation detected by H/D exchange and mass spectrometry. Arch Biochem Biophys 535:115-9

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