Enzyme Catalysis of Electron and Group Transfer

描述（由申请人提供）：本基金支持的研究的长期目标是确定维生素B6 （PLP）、维生素B12（腺苷钴胺素）、s -腺苷甲硫氨酸（SAM）和铁硫簇在酶促反应中的作用的新化学机制。PLP生物学的传统作用是稳定酶促反应中的碳离子中间体。该基金支持的研究的一个主要重点是阐明PLP在催化涉及自由基-顺磁中间体的反应中的作用。plp促进的自由基反应似乎发生在赖氨酸2,3-氨基交换酶和赖氨酸5,6-氨基交换酶等氨基交换酶的反应中。底物和维生素辅酶的自由基中间体将被光谱表征，催化它们的反应的酶的结构将被阐明。SAM和[4Fe-4S]簇在自由基形成过程中的作用将被揭示，并在化学、光谱和动力学上进行表征。探讨腺苷钴胺素在维生素b12依赖酶和SAM/[4Fe-4S]依赖酶中的作用关系。将发现维生素B6和B12、SAM和[4Fe-4S]的新化学作用。新的-氨基酸将通过改造产生氨基交换酶的基因而产生。

DESCRIPTION (provided by applicant): The long term objectives of the research supported by this grant are to determine the novel chemical mechanisms by which vitamin B6 (PLP), Vitamin B12 (adenosylcobalamin), S-adenosylmethionine (SAM), and iron-sulfur clusters function in enzymatic reaction. The conventional role of PLP biology is to stabilize carbanionic intermediates in enzymatic reactions. A major focus of the research supported by this grant is the elucidation of the role of PLP in catalyzing reactions that involve free radical-paramagnetic intermediates. PLP-facilitated radical reactions appear to take place in reactions of aminomutases such as lysine 2,3-aminomutase and lysine 5,6-aminomutase. Radical intermediates of substrates and vitamin coenzymes will be characterized spectroscopically, and the structures of the enzymes that catalyze their reactions will be elucidated. The roles of SAM and [4Fe-4S] clusters in the initiation of radical formation will be unmasked and characterized chemically, spectroscopically, and kinetically. The relationship between the actions of adenosylcobalamin in Vitamin B 12-dependent and SAM/[4Fe-4S]-dependent aminomutases will be explored. Novel chemistry in the actions of vitamins B6 and B12, SAM, and [4Fe-4S] will be discovered. New beta-aminoacids will be produced by engineering of the genes producing aminomutases. Aminomutases are important in amino acid metabolism and the biosynthesis of antibiotics such as Streptothricin F, Myomycin, Blasticidin S, and Taxol. The contributions of beta- amino acids produced by lysine 2,3-aminomutase and arginine 2,3-aminomutase to the functions of antibiotics are not known. The beta-aminoacids may become significant in drug development.