Cleavage Product Accumulation Decreases the Activity of Cutinase during PET Hydrolysis

The Fusarium
solani cutinase (FsC) is a promising candidate
for the enzymatic degradation of the
synthetic polyester polyethylene terephthalate (PET) but still suffers
from a lack of activity. Using atomic MD simulations with different
concentrations of cleavage product ethylene glycol (EG), we show influences
of EG on the dynamic of FsC. We observed accumulation
of EG in the active site region reducing the local flexibility of FsC. Furthermore, we used a coarse-grained mechanical model
to investigate whether substrate binding in the active site causes
an induced fit. We observed this supposed induced fit or “breath-like”
movement during substrate binding indicating that the active site
has to be flexible for substrate conversion. This guides rational
design: mutants with an increased flexibility near the active site
should be considered to compensate the solvent-mediated reduction
in activity.