FIGURE 10.

Ester bond formation by cyclization in TE domains. Final steps of (a) daptomycin, (b) lysobactin, (c) surfactin, and (d) spiruchostatin biosynthesis. For simplicity, only the last two domains of the NRPS systems are represented. Cyclization occurs by nucleophilic attack of a hydroxy group within the acyl‐ester intermediate on its own ester carbon linked to the active site serine. The hydroxy can be located in (a) the side chain of a proteogenic amino acid residue, (b), a β‐hydroxylated amino acid residue (c) a fatty acyl moiety or a (d) polyketide moiety