The effect of imidazolium cations on the structure and activity of the Candida antarctica Lipase B enzyme in ionic liquids

Abstract

In order to understand how cations affect the structural changes and enzyme activity of Lipase B from Candida antarctica, we performed all-atom molecular dynamics simulations of CALB in four types of ionic liquids (ILs) with varying sizes of imidazolium cations and correlated these results with the experimentally determined CALB activity. The imidazolium cations under study differ in the alkyl tail length in the following order: [Emim](+) < [Bmim](+) < [Hmim](+) < [Omim](+). We observed that the best enzyme activity and structural stability of CALB are obtained in [Bmim][TfO] and [Hmim][TfO]. In contrast, in [Emim][TfO], bonding of [TfO](-) to LYS-290 disrupts the interactions between LYS-290 and ILE-285, which leads to a closed catalytic gate conformation with low accessibility of substrates to the catalytic triad. In [Omim][TfO], strong hydrophobic interactions between [Omim](+) and LEU-278 result in a significant loss of the secondary structure of the α-10 helix and cause the exposure of the catalytic triad to ILs, which affects the stability of the catalytic triad and consequently deteriorates the enzyme activity. Overall, our study indicates that a high ion coordination number ([Emim][TfO]) or the presence of a long hydrophobic tail ([Omim][TfO]) can facilitate ion-protein interactions that cause structural distortions and a decrease in CALB enzyme activity in ILs.

Effects of phosphonium‐based ionic liquids on the lipase activity evaluated by experimental results and molecular docking

“…Although most studies are focused on the enzymes catalytic activity in presence of aromatic ILs, particularly imidazolium‐based, noncyclic and nonaromatic cations, such as phosphonium‐based ILs, could lead to relevant improvements and contribute to the design of efficient biotechnological processes . Imidazolium‐based ILs have been applied as solvents in biocatalytic processes involving reactions such as transesterification and hydrolysis . Mai et al studied the transesterification of sugar fatty acids catalyzed by Novozym 435 in presence of imidazolium‐based ILs, showing 96% of conversion of vinyl laurate with glucose in a mixture of (1:1, vol/vol) [C 4 mim][TfO]:[C 4 mim][NTf 2 ] (1‐butyl‐3‐methylimidazolium triflate:1‐butyl‐3‐methylimidazolium bistrisflamide).…”

“…The authors showed that these ILs promote changes in the protein secondary structure leading to a decrease on the enzymatic activity. In general, mainly ILs composed of fluorinated‐based anions and cations with small alkyl chain length were used to maintain or improve the enzymes activity …”

“…[26][27][28] Imidazolium-based ILs have been applied as solvents in biocatalytic processes involving reactions such as transesterification and hydrolysis. [29][30][31][32][33][34] Mai et al 29 (1-butyl-3-methylimidazolium triflate:1-butyl-3-methylimidazolium bistrisflamide). After 10 cycles, the enzyme activity was 75% of its initial activity.…”

“…In general, mainly ILs composed of fluorinated-based anions and cations with small alkyl chain length were used to maintain or improve the enzymes activity. 32,[35][36][37] In addition to the commonly applied imidazolium-based ILs, phosphonium-based counterparts display interesting advantages. These ILs are less expensive, display higher thermal stability, and are available in large quantities, being already applied in industrial processes.…”

Enantioselectivity ofd-amino acid oxidase in the presence of ionic liquids

“…2,6 The correlations between ionic constituents as well as the alkyl chain length of ILs and enzymatic activity and stability have been analysed in detail. 3,[7][8][9] The enzymatic behaviours have been improved in ILs (higher enantioselectivity and better recoverability and recyclability) due to high conversion rates. [10][11][12][13] Interestingly, enzymatic reactions in the presence of ILs have provided useful information on the enzymes exibility and stability, enzyme inhibition, behaviour of enzyme.…”