(253ax) Understanding the Structure and Function of Enzymes in ILs for Improved Biocatalysis

Evaluating the degree to which an enzyme is able to
maintain its structure and function in non-native solvents has widespread
relevance, particularly to the field of biocatalysis. Ionic liquids (ILs)
represent one such category of non-native solvents that have been gaining
ground in recent decades as important solvents for biocatalysis, due to their
low flammabilities and vapor pressures and highly tunable solvent properties. The
discovery that some enzymes are able to maintain a level of function/activity in
ILs has led to large-scale interest in determining the extent of the broadened landscape
of viable biotransformations. Despite this interest, however, progress has been
hindered due to a lack of a molecularly detailed understanding of how to rationally
design enzymes to have increased stability in ILs. Molecular simulation has
proven to be an invaluable tool at providing insight into the atomic level
interactions of enzymes with ILs. Included in this poster are results from molecular
dynamics (MD) simulations of multiple different enzyme/IL systems of interest:
(1) a newly discovered family of enzymes called lytic polysaccharide
monooxygenases (LPMOs) are simulated in three aqueous ILs at 0, 10, and 20
weight percent to evaluate their potential to aid cellulases in the
decomposition of cellulose for conversion into fuels and chemicals, and (2) Bacillus
subtilis lipase A is simulated in aqueous [BMIM][Cl] at 0, 5, 10, and 20
volume percent to evaluate its potential to maintain stability and activity in
ILs for general biocatalysis applications. Structural and dynamic analyses
indicate LPMO enzymes are predicted to be highly stable across the range of IL
solutions tested; however, key areas that deviated from the crystal structures
are identified as a basis for future rational design efforts to increase
stability in ILs through surface charge modifications. Additionally, preferred
binding sites for IL ions on the surface of lipase A are identified and
compared to experimental crystallographic data¹ as a means to
stabilize against IL-induced inactivation.

References

[1] Nordwald, E.; Plaks,
J.; Snell, J.; Sousa, M.; Kaar, J. Crystallographic Investigation of
Imidazolium Ionic Liquid Effects on Enzyme Structure. Chembiochem 2015, 16, 2456-2459.