许多重要的微生物药物由I型聚酮合酶（PKS）合成，酰基转移酶（AT）是其不可或缺的功能域，它负责将酰基底物转移到PKS酰基载体蛋白ACP上，该过程是I型PKS药物合成的首步决速反应，也决定了药物的分子结构，因此深入揭示AT的分子机制具有重要的科学意义和应用价值。本项目以FK506工业菌（链霉菌YN06）的PKS中4个AT（转移不同酰基）为模式研究对象，通过研究AT催化酰基转移过程中底物选择性、底物竞争性、产物抑制效应，阐明AT的催化机理；通过研究AT的酰基特异性模序、催化过程系列复合物晶体构象变化，解析其结构与功能的关系；结合其它原核生物I型PKS进行AT进化分析，研究酰基特异性模序与酰基底物选择性、催化效率之间的关系，阐释原核生物AT的分子进化。同时，基于机制研究改造AT结构，提高其催化活性和底物选择性，并强化合成通路中的前体供应，从而为建立I型PKS微生物药物高效生物合成通路奠定基础。

Many valuable microbial medicines are biosynthesized by type I polyketide synthase (PKS). Acyltransferase (AT) domain plays an essential role to type I PKS via transfer acyl units into acyl carrier proteins (ACP) of PKS. Since incorporation of acyl units into PKS machineries is the first and rate-limiting step of biosynthesis, and determine the sturcture of polyketide,unveiling mechanism of AT under molecular level has great value. In this project, we chose four ATs of FK506 PKS from an industrial producing strain, Streptomyces sp.YN06, as a model to reveal molecular mechanism of AT. This project focus on main contents as following: (i)catalytic mechanism of AT, including substrate specificity, substrate competition, product inhibition, and kinetic assay in the transfer pathway of acyl units; (ii) relationship between structure and function, especially the effects of acyl-specific motif of AT and configuration of intermediates, (iii) evolutionary analysis of AT from different prokaryotes.Our research not only reveal the catalytic mechanism of AT under molecular level, but also may help us to improve the activities and substrate specificity by engineering of AT, resulting in an high efficiency biosynthetic pathway of microbial medicine.