报告时间：2015年9月21日（星期一）上午9:00 

　　报告地点：生物楼学术报告厅 

　　报告人：Prof. Hung-wen LIU, University of Texas at Austin, USA 

　　报告摘要：The Diels–Alder reaction is a [4+2]-cycloaddition reaction in which a cyclohexene ring is formed between a 1,3-diene and an alkene via a single pericyclic transition state. This reaction has been proposed as a key transformation in the biosynthesis of many secondary metabolites. Although several purified enzymes have been implicated in Diels–Alder alike reaction, these enzymes typically demonstrate more than one catalytic activity, leaving their specific influence on the cycloaddition step uncertain. We identified a cyclase, SpnF, that catalyzes a [4+2]-cycloaddition to form the fused cyclohexene ring in spinosyn A, an important insecticide from Saccharopolyspora spinosa. SpnF is unique, because it is the only known enzyme that specifically catalyzes a [4+2]-cycloaddition without introducing any other changes to its substrate. The same cycloaddition also takes place non-enzymatically, but at a much reduced rate. We measured alpha-secondary deuterium kinetic isotope effects at both points of rehybridization in the diene during both enzymatic and non-enzymatic reactions, and demonstrated that SpnF is the first example of a natural Diels-Alderase. 

　　报告人简介：Hung-wen LIU (刘鸿文)博士，美国德克萨斯大学奥斯汀校区药学院及化学与生物化学系终身教授。刘教授出生于台北，在台湾东海大学获学士学位，1981年在哥伦比亚大学获博士学位，导师Koji Nakanishi教授。随后在麻省理工学院Christopher Walsh教授课题组从事博士后工作。1984年到明尼苏达大学化学系工作，1999年成为Distinguished McKnight大学教授。刘教授于2000年转到德克萨斯大学奥斯汀校区，担任George Hitchings Regent Chair讲席教授，任教于药学院及化学与生物化学系。 

　　刘教授的研究兴趣在化学和生物学交叉领域，主要研究重要天然产物生物合成途径中关键酶的催化反应机制。刘教授的研究工作赢得了许多荣誉，包括the NIH Research Career Development Award (1990), the Horace S. Isbell Award (1993), the MERIT Award (1999), the Nakanishi Prize (2007), the Repligen Award (2008), 台湾中央研究院院士 (2008), the A. I. Scott Medal (2011), the Arthur C. Cope Late Career Scholars Award (2014) 和中科院海外评审专家 (2015)。刘教授是美国科学进步协会、美国微生物学会、日本科学促进学会、美国化学学会等专业协会会员以及香港大学、国立清华大学、东海大学等大学名誉教授。刘教授从2004年开始担任Organic Letters杂志副主编。刘教授于2013-2014年担任美国化学会生物学部主席。刘教授课题组已在Science, Nature及其子刊，PNAS和JACS等国际权威学术期刊发表论文240余篇。 

　　报告联系人：1816组，赵宗保（89211）