The S-adenosyl-l-methionine-dependent O-methyltransferases TylE and TylF catalyze the last two methylation reactions in the tylosin biosynthetic pathway of Streptomyces fradiae. It has long been known that the TylE-catalyzed C2″-O-methylation of the 6-deoxy-d-allose bound to demethylmacrocin or demethyllactenocin precedes the TylF-catalyzed C3″-O-methylation of the d-javose (C2″-O-methylated 6-deoxy-d-allose) attached to macrocin or lactenocin. This study reveals the unexpected substrate promiscuity of TylE and TylF responsible for the biosynthesis of d-mycinose (C3″-O-methylated d-javose) in tylosin through the identification of a new minor intermediate 2″-O-demethyldesmycosin (2; 3″-methyl-demethyllactenocin), which lacks a 2″-O-methyl group on the mycinose moiety of desmycosin, along with 2″-O-demethyltylosin (1; 3″-methyl-demethylmacrocin) that was previously detected from the S. fradiae mutant containing a mutation in the tylE gene. These results unveil the unique substrate flexibility of TylE and TylF and demonstrate their potential for the engineered biosynthesis of novel glycosylated macrolide derivatives.
Bibliographical noteFunding Information:
We thank Prof. Eric Cundliffe for providing tylosin intermediates and Dr. Kris Rathwell for critically reading this manuscript. This work was supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (MISP) (2016R1A2A1A05005078), the Intelligent Synthetic Biology Center of the Global Frontier Project funded by MISP (20110031961), Advanced Production Technology Development Program, Ministry of Agriculture, Food and Rural Affairs, and High Value-added Food Technology Development Program, Ministry of Agriculture, Food and Rural Affairs, Republic of Korea. M.C.S. was supported by RP-Grant 2016 from Ewha Womans University.
© 2016 The American Chemical Society and American Society of Pharmacognosy.