Regulation of Phenylalanine Catabolism

描述（由申请人提供）：肝酶苯丙氨酸羟化酶负责分解日粮中过量苯丙氨酸。该酶水平的缺乏导致代谢紊乱苯丙酮尿症，如果不治疗，这种疾病会造成毁灭性的神经系统后果，这证明了该酶在生理上的重要性。苯丙氨酸羟化酶的核心功能是通过其底物，苯丙氨酸和四氢生物蝶呤以及磷酸化来调节酶。这两种形式的调控都需要n端~117残基调控域。在普遍接受的调节模型中，酶的静止形式是无活性的，在调节位点上苯丙氨酸的变构结合将酶转化为活性形式。四氢生物蝶呤稳定了非活性形式，而磷酸化则增强了向活性形式的转化。本文提出的研究目标是了解变构调节的结构和动力学基础。拟议的实验将结合现代结构方法（例如，核磁共振和质谱）与结合和催化的内在速率常数的测量，以便对苯丙氨酸羟化酶的变构调节提供更完整的理解。

DESCRIPTION (provided by applicant): 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.