The manuscript by Fellner et al. targets the structural characterization of the FphI protein, including some substrate specificity efforts for this protein. Overall, the work is fundamental when it comes to characterizing this new protein. I would have expected the study to do more toward: mechanism of catalysis (considering the high structural resolution obtained in their study for FphI) and kinetic characterization of FphI and comparison to FphH to explore further the similarities and distinction between these two proteins; such as determination of kcat and Km. Moreover, mutagenesis studies should have been considered to further evaluate the significance of structural differences between these two residues; could FphH be ‘converted into FphI through mutagenesis?
Minor point:
Line 58, should be Figure 1B not 1A.
Line 16-19: Note that in the context of this study hydrolases are targeted for development of antibacterial agents, not as diagnostic tools. Both sentences have to be corrected.