Melançon Charles E, Liu Hung-Wen
Division of Medicinal Chemistry, College of Pharmacy, University of Texas at Austin, Austin, Texas 78712, USA.
J Am Chem Soc. 2007 Apr 25;129(16):4896-7. doi: 10.1021/ja068254t. Epub 2007 Mar 28.
Previous pathway engineering work demonstrated that the desosamine biosynthetic pathway in could be converted to an efficient mycaminose biosynthesizing pathway by replacement of DesI with the hexose 3,4-ketoisomerase Tyl1a. In this work, FdtA, a ketoisomerase homologous to Tyl1a which catalyzes conversion of the Tyl1a substrate to the C-4 epimer of the Tyl1a product was used to replace DesI. The ability of desosamine pathway enzymes DesV, DesVI, DesVII, and DesVIII to accept substrates with inverted C-4 stereochemistry in the mutant expressing FdtA resulted in formation of macrolide derivatives bearing 4--D-mycaminose, a sugar heretofore unobserved in Nature. Interestingly, minor glycosylated macrolides bearing another non-natural sugar, 3--monomethylamino-3-deoxy-D-fucose, were also produced by this mutant. An explanation for the formation of these unexpected new compounds is presented, and the implications of this work for combinatorial biosynthesis of new antibiotics are discussed.
先前的途径工程研究表明，通过用己糖3,4-酮异构酶Tyl1a替代DesI，[具体微生物名称]中的去氧氨基糖生物合成途径可以转化为高效的霉胺糖生物合成途径。在这项工作中，使用了与Tyl1a同源的酮异构酶FdtA来替代DesI，FdtA催化Tyl1a底物转化为Tyl1a产物的C-4差向异构体。在表达FdtA的突变体中，去氧氨基糖途径的酶DesV、DesVI、DesVII和DesVIII接受具有相反C-4立体化学结构底物的能力，导致形成了带有4--D-霉胺糖的大环内酯衍生物，这是一种迄今在自然界中未观察到的糖。有趣的是，该突变体还产生了带有另一种非天然糖3--单甲基氨基-3-脱氧-D-岩藻糖的少量糖基化大环内酯。本文对这些意外新化合物的形成给出了解释，并讨论了这项工作对新型抗生素组合生物合成的意义。
