Fig 4.

Proposed amicetin biosynthesis pathway. (A) Proposed biosynthesis of two deoxysugars. (B) Two proposed alternative strategies for amide bond formation in amicetin biosynthesis. The dashed-line arrows denote biosynthesis steps predicted solely from bioinformatic analyses, and the solid-line arrows represent biosynthesis steps based on data from in vivo gene inactivation experiments. The orders for sugar attachments are deduced from the accumulation of compound 17 in the ΔamiF mutant AM1003 and the ΔamiL mutant AM1007 (Fig. 5). Sugar attachments can also occur after the formation of the two amide bonds. X, domain with unknown function; A, adenylation domain; PCP, peptidyl carrier protein.