How a protein can remain stable in a solvent with high content of urea: Insights from molecular dynamics simulation of Candida antarcetica lipase B in urea:choline chloride deep eutectic solvent

نویسنده:
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سال
: 2014
چکیده: Deep eutectic solvents (DESs) are utilized as green and inexpensive alternatives to the

classical ionic liquids. It was known that some of DESs can be used as solvent in the

enzymatic reactions to obtain very green chemical processes. DESs are almost poorly

understood at the molecular level. Moreover, we do not know much about the enzyme

microstructure in such systems. For example, how some hydrolase can remain active and

stable in a deep eutectic solvent including 9M of urea? In this study, molecular dynamic of

DESs as a liquid has been simulated at the molecular level. Urea: Choline chloride as a well-known eutectic mixture was chosen as model DESs. Behavior of the lipase as a biocatalyst

was studied in this system. For comparison, the enzyme structure was also simulated in urea

8M. Thermal stability of the enzyme was also evaluated in DESs, water, and urea 8M. The

enzyme showed very good conformational stability in urea:choline chloride mixture with

about 66% urea (9M) even at high temperatures. The results are in good agreement with

recent experimental observations. In contrast, complete enzyme denaturation occurred in urea

8M with only 12% urea in water. It was found that urea molecules denature the enzyme by

interrupting the intra-chain hydrogen bonds in a “direct denaturation mechanism”. However,

in urea:choline chloride deep eutectic solvent, as a result of hydrogen bonding with choline

and chloride ions, urea molecules have a low diffusion coefficient and cannot reach to the

protein domains. Interestingly, urea, choline, and chloride ions form hydrogen bonds with the

surface residues of the enzyme which, instead of lipase denaturation, leads to more enzyme

stability. To the best of our knowledge, this is the first study in which the microstructural

properties of a macromolecule are examined in a deep eutectic solvent.
کلیدواژه(گان): Deep eutectic solvents,Simulation,enzyme,urea
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