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个不寻常的黄素单甘肽（FMN）依赖酶，II型异戊烯基二磷酸（IPP）异构酶的克隆和初步表征。IPP异构酶使异戊烯基二磷酸和二甲基烯丙基二磷酸相互转化，这是一系列生物类异戊二烯化合物的代谢构件。新鉴定的II型酶代表了一种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，并且不存在于人类中。对II型IPP异构酶的初步研究表明，催化需要FMN和NADPH。这两种辅因子的作用尚不清楚，因为异构化不需要净氧化/还原，并且I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。本研究旨在阐明这两个辅因子的功能、化学机制以及活性位点残基在集胞藻6803的II型异戊烯基二磷酸异构酶催化反应中的作用。

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.