FIGURE 16.

Proposed biosynthesis of cereulide, valinomycin and a hypothetical product from Bacillus stratosphericus LAMA 585. (a) During elongation ester bonds are formed by C₃ domains. During termination, the TE domains catalyzes oligomerization of tetradepsipeptidyl units, as well as cyclic release, using the distal α‐hydroxy groups as nucleophiles (see also Figure 17). (b) Depsipeptide Modules 1 and 3 activate, thiolate and reduce α‐keto acids to generate α‐hydroxy acyl thioesters. Adapted from Alonzo et al. ³⁴