Mechanism of remarkable peptide modifications by the multinuclear non-heme iron-dependent oxidative enzymes ChrH/DybH

DybH catalyzes a conserved two-cysteine peptide motif rearrangement that forms a macrocycle and a hydantoin heterocycle, with oxidation to a thioaldehyde as the first step.

• Why it matters: MNIOs perform difficult peptide oxidations, but the sequence of chemical steps for cysteine-modifying enzymes like DybH and ChrH is poorly understood.
• What they did: Using substrate and active-site mutations in the DybH system, the authors analyzed modified products, including a cysteine-to-formylglycine outcome and shunt products lacking the macrocycle.
• The result: Active-site mutations support thiol oxidation to a thioaldehyde first, while substrate cysteine mutations indicate macrocyclization occurs in the final step, yielding mechanistic snapshots.