Figure 1.

Mupirocin biosynthesis. The C₁₇ monic acid backbone is assembled by MmpD, MmpA and MmpE. Esterification of the C₁₇ pre‐monic acid backbone (3) with the fatty acid chain (shown is the full length 9‐hydroxynonanoic acid thiol ester (2)) and tetrahydropyran ring (THP) formation yields PA‐B. PA‐B is subsequently converted to PA‐A (1) in a further multistep cascade. Accumulation of both mupiric acid and mupirocin H is observed when specific mutations in mmpD or mmpA are made and importantly also when late‐stage enzymes are inactivated. ACP—acyl carrier protein, AT—acyl transferase, ER—enoylreductase, DH—dehydratase, KR—ketoreductase, KS—ketosynthase, MT, methyl transferase, Ox—oxidoreductase, TE—thioesterase.