Further mutating W77 into H and Q did not restore the activity, while only partially restored in W77F and W77Y mutants, indicating the importance of hydrophobicity at this position (Supplementary Figure ). Moreover, although S187 and Y152 in MicA correspond to Y197 and F162 in Bnd4 and Y214 and Y178 in AlbS , alanine mutations toward these two residues did not result in the previously observed product profile change. Instead, the mutations led to primary product enhancement (S187A) or elimination (Y152A) (Fig. ).