Polymer-based protein engineering (PBPE) offers an attractive method to predictably modify and
enhance enzyme structure and function. Using polymers that respond to stimuli such as temperature and
pH, enzyme activity and stability can be predictably modified without a dependence on molecular
biology.
Herein, we demonstrate that temperature responsive enzyme-polymer conjugates show
increased stability while retaining bioactivity and substrate affinity. The bioconjugates were synthesized
using a “grafting from” approach, where polymers were grown from a novel water-soluble initiator on
the surface of a protein using atom transfer radical polymerization. Prior to polymer synthesis, the
polymerization initiating molecule was covalently attached to surface accessible primary amines (lysine,
N-terminal) of chymotrypsin, forming a macroinitiator. Poly(N-isopropylacrylamide) and poly[N,N’-
dimethyl(methacryloylethyl) ammonium propane sulfonate] were grown separately from the initiator
modified chymotrypsin. Both polymers were selected because of their temperature-dependent conformations.
We observed that the enzyme-polymer conjugates retained temperature-dependent changes in
conformation while still maintaining enzyme function. The conjugates exhibited dramatic increases in
enzyme stability over a wide range of temperatures. We can now predictably manipulate enzyme kinetics
and stability using polymer-based protein engineering without the need for molecular biology
dependent mutagenesis.