Involved in the biosynthesis of mycarose which is a 6-deoxyhexose sugar required during production of the macrolide antibiotic tylosin. Catalyzes the transfer of L-mycarosyl from dTDP-beta-L-mycarose to demethyllactenocin to yield demethylmacrocin. demethyllactenocin + dTDP-beta-L-mycarose = demethylmacrocin + dTDP + H(+) Cells lacking this gene accumulate desmycosin (tylosin B). Belongs to the UDP-glycosyltransferase family.