Identification of plant peroxidases catalyzing the degradation of
polyfluorinated aromatics using a peroxidase library approach
Abstract
In this work, the degradation of mono- and polyfluorinated phenolic
compounds was demonstrated by a series of crude plant peroxidases,
including horseradish root and 6 members of the cucurbita genus. Highly
active samples were identified using a library screening approach in
which more than 50 crude plant samples were initially evaluated for
defluorination activity toward 4-fluorophenol. The highest
concentrations were observed in the horseradish root (HRP), pumpkin skin
(PKS), and butternut squash skin (BNS), which consistently gave the
highest intrinsic rates of decomposition for all the substrates tested.
While HRP exhibited a significant decrease in activity with increased
fluorination of the phenolic substrate, PKS showed only minor
reductions. Furthermore, in silico studies indicated that the active
site of HRP poorly accommodates the steric bulk of additional fluorines,
causing the substrate to dock farther from the catalytic heme and thus
slowing the catalysis rate. We propose that the PKS active site might be
larger, allowing closer access to the perfluorinated substrate, and
therefore maintaining higher activity compared to the HRP enzyme.
However, detailed kinetic characterization studies of the peroxidases
are recommended. Conclusively, the high catalytic activity of PKS and
its high yield per gram of tissue make it an excellent candidate for
developing environmentally friendly biocatalytic methods for degrading
fluorinated aromatics. Finally, the success of the library approach in
identifying highly active samples for PFAC degradation suggests the
method may find utility in the quest for other advanced catalysts for
PFAS degradation