Mechanistic Studies of Type II IPP Isomerase

描述（由申请人提供）： 最近的一份报告描述了一种不寻常的黄素单核苷酸 (FMN) 依赖性酶，即 II 型异戊烯基二磷酸 (IPP) 异构酶的克隆和初步表征。 IPP 异构酶可将异戊烯基二磷酸和二甲基烯丙基二磷酸相互转化，这是多种生物类异戊二烯化合物的代谢结构单元。新发现的 II 型酶代表了一个有吸引力的抗菌药物靶点，因为序列分析表明它在病原体金黄色葡萄球菌中是必需的，但在人类中不存在。对 II 型 IPP 异构酶的初步研究表明，催化作用需要 FMN 和 NADPH。鉴于异构化并不需要净氧化/还原并且l型异构酶催化不包括瞬时氧化/还原的质子加成-质子消除反应，这两个辅因子的作用尚不清楚。这项工作旨在阐明两个辅因子的功能、化学机制以及活性位点残基在集胞藻 II 型异戊烯基二磷酸异构酶催化的反应中的作用。 PCC 6803。

DESCRIPTION (provided by applicant): A recent report describes the cloning and preliminary characterization of an unusual flavin mononucleotide (FMN) dependent enzyme, the type II isopentenyl diphosphate (IPP) isomerase. IPP isomerases interconvert isopentenyl diphosphate and dimethylallyl diphosphate, the metabolic building blocks for a wide array of biological isoprenoid compounds. The newly identified type II enzyme represents an attractive antimicrobial drug target as sequence analyses suggest that it is essential in the pathogen Staphylococcus aureus and is not present in humans. The initial study with the type II IPP isomerase indicated that catalysis requires both FMN and NADPH. The role is these two cofactors is unclear, given that isomerization does not entail a net oxidation/reduction and that the type l isomerase catalyzes a proton addition-proton elimination reaction that does not include a transient oxidation/reduction. This proposed work intends to elucidate the functions of the two cofactors, the chemical mechanism, and the roles of active site residues in the reaction catalyzed by type II isopentenyl diphosphate isomerase from Synechocystis sp. PCC 6803.