Involved in the biosynthesis of the complex macrolide antibiotic tylosin. Catalyzes the hydroxylation of 20-oxo-5-O-beta-mycaminosyltylactone at the C-23 position to yield 5-O-beta-mycaminosyltylonolide. 20-oxo-5-O-beta-D-mycaminosyltylonolide + 2 H(+) + O2 + 2 reduced [2Fe-2S]-[ferredoxin] = 5-O-beta-D-mycaminosyltylonolide + H2O + 2 oxidized [2Fe-2S]-[ferredoxin] Antibiotic biosynthesis; tylosin biosynthesis. Cells lacking this gene are blocked in the monooxygenation of tylactone at position C-23 and accumulate 20-oxo-5-O-beta-mycaminosyltylactone. Belongs to the cytochrome P450 family. Extended N-terminus.