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.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-BCMB-B (03))
Program Officer
Gerratana, Barbara
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Texas Health Science Center San Antonio
Schools of Medicine
San Antonio
United States
Zip Code
Khan, Crystal A; Fitzpatrick, Paul F (2018) Phosphorylation of Phenylalanine Hydroxylase Increases the Rate Constant for Formation of the Activated Conformation of the Enzyme. Biochemistry 57:6274-6277
Zhang, Shengnan; Fitzpatrick, Paul F (2016) Identification of the Allosteric Site for Phenylalanine in Rat Phenylalanine Hydroxylase. J Biol Chem 291:7418-25
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 476:457-461
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, 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
Fitzpatrick, Paul F (2015) Structural insights into the regulation of aromatic amino acid hydroxylation. Curr Opin Struct Biol 35:1-6
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; 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
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

Showing the most recent 10 out of 12 publications