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学术报告

【启智讲坛第二十四讲】Mechanistic Investigation of the Cycloaddition Catalyzed by SpnF

主要完成人: 发表日期:2017-05-12 点击数:266

 微生物代谢国家重点实验室启智讲坛第二十四讲暨国重实验室科技创新训练课程
 
 
 
报告题目:Mechanistic Investigation of the Cycloaddition Catalyzed by SpnF
 
 
主讲人:Hung-wen Liu

Elected Academician of Academia Sinica

American Academy of Microbiology Fellow

American Chemical Society Fellow

The University of Texas at Austin

  间:20170516日(星期二) 13:15-14:20

  点:闵行校区生物药学楼树华多功能厅(800号)

Abstract/报告摘要:

SpnF is a polyketide tailoring enzyme in the biosynthetic pathway of the insecticide spinosyn A produced by Saccaropolyspora spinosa. SpnF was the first reported enzyme that specifically catalyzes a [4+2]-cycloaddition without introducing any other changes to its substrate. The same cycloaddition also takes place nonenzymatically, but at a much reduced rate. If the reaction catalyzed by SpnF is a concerted process with a single pericyclic transition state, then SpnF would be the first example of a naturally selected Diels-Alderase. In order to investigate this possibility, α-secondary deuterium kinetic isotope effects were measured at both points of rehybridization in the diene during both the nonenzymatic and SpnF-catalyzed [4+2]-cycloaddition reactions. This was accomplished using regiospecifically deuterated substrates and electrospray ionization, time-of-flight mass spectrometry to follow changes in deuterium enrichment of the substrate as the reaction progressed. The presentation will describe the methodology and theory underlying the measurement of these KIEs, address the key challenges regarding these measurements and offer a mechanistic discussion of their implications for understanding the SpnF catalyzed [4+2]-cycloaddition.