We show that the incorporation of a redox active tyrosine residue at position 121 in SyrB2 results in further post-translational modification to DOPA. This DOPA residue binds ferric iron with very high affinity and results in a catalytically inactive, off-cycle enzymatic species. The ferric-DOPA species likely forms as a result of an unproductive oxidation in F121Y-SyrB2 (Scheme 1). After H-atom abstraction of the hydroxyl group of Y121, the newly formed hydroxyl group on the iron center will rebound and incorporate into the ring structure, eventually forming DOPA121. This residue can become deprotonated and bind ferric iron from the cellular environment, forming the blue-green chromophore we observe upon purification of this protein (Fig. ). To avoid such unproductive oxidations, halogenases tend to keep redox-inactive residues in their SCS, especially in position 121. The placement of redox-inactive residues in the halogenases is especially important due to multiple isomers of ferryl intermediates, as compared to the hydroxylases. This study also explores the function of H-bonding in the active sites of halogenases, and their implications on catalysis. Our results serve as a warning to others attempting to engineer non-heme iron enzymes for non-native functions, as placement of redox-active residues can result in catalytically non-functional enzymes. No discernable shift in the UV-spectrum is observed implying that DOPA is occupying the halide binding position.