Fig. 7
From: Insights into a dual function amide oxidase/macrocyclase from lankacidin biosynthesis
Proposed mechanism of the LkcE-catalyzed reaction. LC-KA05 binds into the active site, and undergoes FAD-catalyzed oxidation to yield the iminium ion. A conformational change then occurs to bring the δ-lactone in proximity to the iminium, with the new LC-KA05 conformation potentially stabilized by interaction with R326. The final step is an intramolecular Mannich reaction, involving general base catalysis by E64 to generate the nucleophilic C-2 enolate
