Understanding Structure−Stability Relationships of Candida antartica Lipase B in Ionic Liquids

Abstract

Two different water-immiscible ionic liquids (ILs), 1-ethyl-3-methylimidizolium bis(trifluoromethylsulfonyl)imide and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide, were used for butyl butyrate synthesis from vinyl butyrate catalyzed by Candida antarctica lipase B (CALB) at 2% (v/v) water content and 50 degrees C. Both the synthetic activity and stability of the enzyme in these ILs were enhanced as compared to those in hexane. Circular dichroism and intrinsic fluorescence spectroscopic techniques have been used over a period of 4 days to determine structural changes in the enzyme associated with differences in its stability for each assayed medium. CALB showed a loss in residual activity higher than 75% after 4 days of incubation in both water and hexane media at 50 degrees C, being related to great changes in both alpha-helix and beta-strand secondary structures. The stabilization of CALB, which was observed in the two ILs studied, was associated with both the maintenance of the 50% of initial alpha-helix content and the enhancement of beta-strands. Furthermore, intrinsic fluorescence studies clearly showed how a classical enzyme unfolding was occurring with time in both water and hexane media. However, the structural changes associated with the incubation of the enzyme in both ILs might be attributed to a compact and active enzyme conformation, resulting in an enhancement of the stability in these nonaqueous environments.

Enhancement of stability of a lipase by subjecting to three phase partitioning (TPP): structures of native and TPP-treated lipase from Thermomyces lanuginosa

“…In order to open up the substrate binding cleft, the enzyme must be exposed to highly hydrophobic agents such as lipid aggregates or detergents. The substrate binding site has been shown to adopt an open conformation in the presence of detergents [41,42]. Under the influence of aggregated lipid bilayer or detergents, Wall-2 moves away from Wall-1 so that the cleft adopts an open conformation as a result of which the diffusion of substrates can occur into the cleft leading to the required interactions with the active site residues.…”

Effect of Glycosylation of β-Glucuronidase on its Catalytic Properties in Ionic Liquids

“…Given their structure and diversity of functionality, they are capable of providing various types of interactions (e.g., dispersive, ð-ð, n-ð, hydrogen bonding, dipolar, ionic/charge-charge). With increasing [BMIM] PF 6 volumetric ratio, the interactions between anion and enzyme becomes stronger, and this may cause a great conformational change to the enzyme, thus affecting enzyme activity [38][39][40][41][42] . Besides, due to the hydrophilic nature of PGUS-P, it gains a low solubility in the hydrophobic ionic liquids, which may also affect the enzyme catalysis.…”

Development of efficient processes under flow conditions based on catalysts immobilized onto monolithic supported ionic liquid-like phases

“…The immobilization of the enzyme was performed by simple adsorption from an aqueous solution of CALB. The resulting enzymatic catalysts (m-SILLP-11-CALB) showed a very large IL/enzyme ratio, which ensured a full interaction between both enzyme and protein molecule and the IL phase, and could favor the enzyme stabilization [39]. m-SILLPs not only provide high flow characteristics and mechanical stability, based on the intrinsic properties of these macroporous materials, but also an easy and simple protocol to anchor the enzyme onto a modified matrix with "enzyme-friendly" moieties like alkyl-imidazolium cations.…”