Regulation of Phenylalanine Catabolism

说明(申请人提供)：肝酶苯丙氨酸羟基酶负责分解饮食中过量的苯丙氨酸。这种酶水平的不足会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，证明了这种酶的生理重要性。苯丙氨酸羟基酶正常功能的核心是通过其底物苯丙氨酸和四氢生物蝶呤以及通过磷酸化来调节该酶。这两种形式的调控都需要N-末端~117残基的调节域。在普遍接受的调节模型中，酶的休眠形式是非活性的，而苯丙氨酸在调节部位的变构结合将酶转化为活性形式。四氢生物蝶呤稳定非活性形式，而磷酸化加强向活性形式的转化。这项研究的目的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(如核磁共振和质谱学)与结合和催化的本征速率常数的测量，以提供更全面的了解苯丙氨酸羟基酶的变构调节。 公共卫生相关性：这是一项研究肝酶苯丙氨酸羟基酶调节的建议。这种酶的遗传缺陷，除非受影响的人从出生起就被限制饮食。更好地理解这一规定将提高我们开发更好的PKU治疗方法的能力。

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.