Fig. 1
Biosynthesis and structures of fungal CDPs. a Proposed biosynthesis of fungal CDPs. The d-hydroxycarboxylic acid is activated by module 1, while the l-amino acid is activated and methylated by module 2. Both substrates are coupled until a hexa- or octapeptidol is formed. Release from the enzyme at the C3 domain occurs under cyclization. According to the “parallel” model, elongation of the depsipeptide chain occurs by the addition of dipeptidol units. In the “linear” or “looping” model, single building blocks are attached to the growing depsipeptide chain, which is shuttled between the PCP1 and PCP2a/b domains. b Structures of enniatin B, beauvericin, bassianolide and PF1022