Mechanistic Insight into Peptidyl‐Cysteine Oxidation by the Copper‐Dependent Formylglycine‐Generating Enzyme

Abstract

AbstractThe copper‐dependent formylglycine‐generating enzyme (FGE) catalyzes the oxygen‐dependent oxidation of specific peptidyl‐cysteine residues to formylglycine. Our QM/MM calculations provide a very likely mechanism for this transformation. The reaction starts with dioxygen binding to the tris‐thiolate CuI center to form a triplet CuII‐superoxide complex. The rate‐determining hydrogen atom abstraction involves a triplet‐singlet crossing to form a CuII−OOH species that couples with the substrate radical, leading to a CuI‐alkylperoxo intermediate. This is accompanied by proton transfer from the hydroperoxide to the S atom of the substrate via a nearby water molecule. The subsequent O−O bond cleavage is coupled with the C−S bond breaking that generates the formylglycine and a CuII‐oxyl complex. Moreover, our results suggest that the aldehyde oxygen of the final product originates from O2, which will be useful for future experimental work.