Department of Chemistry, Fudan University , Shanghai 200433, China.
J Am Chem Soc. 2018 Jan 31;140(4):1365-1371. doi: 10.1021/jacs.7b10501. Epub 2018 Jan 19.
Regiospecific dehydration of vicinal diols by enzymes is a difficult reaction that usually requires activation by dedicated organic cofactors. The enzymatic use of radical-based chemistry is an effective but challenging alternative as radical intermediates are difficult to control. Here we report the X-ray structure of the radical S-adenosyl-l-methionine (SAM) dehydratase AprD4 involved in the biosynthesis of the aminoglycoside (AG) antibiotic apramycin. Using in vitro characterizations and theoretical calculations based on our crystal structure, we have been able to propose a detailed mechanism of AprD4 catalysis, which involves a complex partially substrate-induced proton relay network in the enzyme active site and highlights the key role of the protein matrix in driving high-energy intermediates.
酶促邻二醇的区域选择性脱水是一种困难的反应，通常需要专用有机辅因子的激活。基于自由基的化学的酶法使用是一种有效的但具有挑战性的替代方法，因为自由基中间体难以控制。在这里，我们报告了参与氨基糖苷（AG）抗生素安普霉素生物合成的自由基 S-腺苷-L-甲硫氨酸（SAM）脱水酶 AprD4 的 X 射线结构。通过使用基于我们晶体结构的体外特性和理论计算，我们能够提出 AprD4 催化的详细机制，该机制涉及酶活性位点中复杂的部分底物诱导质子传递网络，并突出了蛋白质基质在驱动高能中间体中的关键作用。
