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The Evolution of a Catalytic Mechanism

时间:2017年04月07日 16:06 发布人: 浏览次数:[]

[责任编辑]江倩倩 [信息提供]生命学院  

报告题目:The Evolution of a Catalytic Mechanism   

报告时间:2017年4月10日(周一)上午9:30   

报告地点:闵行校区生物药学楼2-116会议室   

报告人:Prof. Antony Michael Dean
      Department of Ecology, Evolution and Behavior,University of Minnesota   

联系人:冯雁  yfeng2009@sjtu.edu.cn

报告内容简介:

  The means by which superfamilies of specialized enzymes arise by gene duplication and functional divergence are poorly understood. The escape from adaptive conflict hypothesis, which posits multiple copies of a gene encoding a primitive inefficient and highly promiscuous generalist ancestor, receives support from experiments showing that resurrected ancestral enzymes are indeed more substrate-promiscuous than their modern descendants. Here, we provide evidence in support of an alternative model, the innovation–amplification–divergence hypothesis, which posits a single-copied ancestor as efficient and specific as any modern enzyme. We argue that the catalytic mechanisms of plant esterases and descendent acetone cyanohydrin lyases are incompatible with each other (e.g., the reactive substrate carbonyl must bind in opposite orientations in the active site). We then show that resurrected ancestral plant esterases are as catalytically specific as modern esterases, that the ancestor of modern acetone cyanohydrin lyases was itself only very weakly promiscuous, and that improvements in lyase activity came at the expense of esterase activity. These observations support the innovation–amplification–divergence hypothesis, in which an ancestor gains a weak promiscuous activity that is improved by selection at the expense of the ancestral activity, and not the escape from adaptive conflict in which an inefficient generalist ancestral enzyme steadily loses promiscuity throughout the transition to a highly active specialized modern enzyme.   

 

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