GENOMIC ENZYMOLOGY: OMP DECARBOXYLASE SUPRAFAMILY

描述(申请人提供)：我们想了解(β/α)8桶折叠功能多样性的结构来源，这是酶中最常见的折叠。我们已经确定了一组同源的(β/α)8桶折叠酶，它们催化与不相关底物的反应，并在不同的代谢途径中发挥作用。Orotidine 5‘-磷酸脱羧酶(OMPDC)是这个超家族中最具特征的成员。我们建议确定OMPDC超家族其他成员的结构/功能关系，以便我们能够理解使用同源支架催化无关反应的结构策略。这些研究极大地扩展了功能多样性的范围，超越了机械上不同的酶超家族，例如烯醇酶和巴豆酶超家族，在这些超家族中，同源酶催化共享共同部分反应的不同反应。这四个具体目标整合了力学和结构研究：力学研究将在Gerlt博士在伊利诺伊州(P.I.)的实验室进行；结构研究将在Rayment博士在威斯康星州(Co-P.I.)的实验室进行： 1)3-酮-L-古龙酸6-磷酸脱羧酶的结构/功能关系将被建立，该酶催化依赖于镁离子的β-酮酸通过二醇类中间体进行脱羧基反应。2)将建立D-阿拉伯-十六-3-果糖-6-磷酸合成酶的结构/功能关系，该合成酶通过烯二酚中间体催化依赖于镁的羟醛缩合反应。3)D-核酮糖-5-磷酸-3-差向异构酶的结构/功能关系将被建立，该酶通过二烯二酚中间体催化二价非金属1，1-质子转移。4)将测试((贝塔/阿尔法)8桶褶皱)功能多样性的结构蓝图。

DESCRIPTION (provided by applicant): We want to understand the structural origins of functional diversity in the (beta/alpha)8 barrel fold, the most commonly observed fold in enzymes. We have identified a group of homologous (beta/alpha)8-barrel fold enzymes that catalyze reactions with unrelated substrates and mechanisms in different metabolic pathways. Orotidine 5'-phosphate decarboxylase (OMPDC) is the best characterized member of this "suprafamily." We propose to determine structure/function relationships for other members of the OMPDC suprafamily so that we can understand the structural strategies for using a homologous scaffold to catalyze unrelated reactions. These studies significantly expand the scope of functional diversity beyond those found in mechanistically diverse enzyme superfamilies, e.g., the enolase and crotonase superfamilies, in which homologous enzymes catalyze different reactions that share a common partial reaction. The four Specific Aims integrate mechanistic and structural studies: the mechanistic studies will be performed in Dr. Gerlt's laboratory at Illinois (P.I.); the structural studies will be performed in Dr. Rayment's laboratory at Wisconsin (Co-P.I.): 1) Structure/function relationships will be established for 3-keto-L-gulonate 6-phosphate decarboxylase that catalyzes Mg2+-dependent decarboxylation of beta-ketoacids via an enediolate intermediate. 2) Structure/function relationships will be established for D-arabino-hex-3-ulose 6-phosphate synthase that catalyzes Mg2+-dependent aldol condensation via an enediolate intermediate. 3) Structure/function relationships will be established for D-ribulose 5-phosphate 3-epimerase that catalyzes divalent metal-independent 1,1-proton transfer via an enediolate intermediate. 4) A structural blueprint for functional diversity in the ((beta/alpha)8-barrel fold will be tested.