Functionally Distinct Modules Operate Two Consecutive α,β→β,γ Double‐Bond Shifts in the Rhizoxin Polyketide Assembly Line

Shift work: Biochemical analysis of the rhizoxin pathway revealed that the diene moiety is not shifted all at once, but through distinct enzymatic operations. The first shift occurs by a formal β,γ-dehydration in module 7, while the second double bond is first generated by module 8 and then shifted by an unprecedented “shift module” with a novel type of DH* domain (see scheme). ACP=acyl carrier protein, DH*=dehydratase-like shift domain.