GENOMIC ENZYMOLOGY: OMP DECARBOXYLASE SUPRAFAMILY

描述（由申请人提供）：我们希望了解（β/α）8桶折叠（酶中最常见的折叠）中功能多样性的结构起源。我们已经确定了一组同源（β/α）8桶折叠酶，催化反应与不相关的底物和机制在不同的代谢途径。乳清酸核苷5 '-磷酸脱羧酶（OMPDC）是该“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不相关反应的结构策略。这些研究显著地扩展了功能多样性的范围，超出了在机械上不同的酶超家族中发现的那些，例如，烯醇化酶和巴豆酸酶超家族，其中同源酶催化共享共同部分反应的不同反应。四个具体目标整合了机械和结构研究：机械研究将在伊利诺伊州Gerlt博士的实验室（P.I.）进行;结构研究将在威斯康星州Rayment博士的实验室（Co-P.I.）进行： 1)将建立3-酮基-L-古洛糖酸6-磷酸脱羧酶的结构/功能关系，该酶通过烯二醇中间体催化β-酮酸的Mg 2+依赖性脱羧。2)将建立D-阿拉伯糖-己-3-酮糖-6-磷酸合酶的结构/功能关系，该合酶通过烯二醇中间体催化Mg 2+依赖性羟醛缩合。3)将建立D-核酮糖5-磷酸3-差向异构酶的结构/功能关系，该酶通过烯二醇盐中间体催化二价金属非依赖性1，1-质子转移。4)将测试（（β/α）8桶折叠中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.