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Ionic Liquid‐Inspired Cations Covalently Bound to Formate Dehydrogenase Improve its Stability and Activity in Ionic Liquids
Author(s) -
Bekhouche Mourad,
Blum Loïc J.,
Doumèche Bastien
Publication year - 2011
Publication title -
chemcatchem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.497
H-Index - 106
eISSN - 1867-3899
pISSN - 1867-3880
DOI - 10.1002/cctc.201000390
Subject(s) - formate dehydrogenase , ionic liquid , chemistry , azide , biocatalysis , formate , catalysis , inorganic chemistry , organic chemistry , combinatorial chemistry
Abstract Ionic liquids (ILs) are important new solvents for electrochemistry and biocatalysis, but dehydrogenases usually do not work in ionic liquids. Adding more than 40 % (v/v) of the water miscible ionic liquid [MMIm][Me 2 PO 4 ] (MMIm: 1‐methyl‐3‐methyl imidazolium dimethylphosphate) inactivates the formate dehydrogenase (FDH) from Candida boidinii . The grafting of a variety of IL‐inspired hydroxylated cations (hydroxyalkyl imidazolium, hydroxylalkyl pyrrolydinium, and cholinium) on the enzyme through lysine coupling was performed to understand the relationship between grafted cation, enzyme activity, and protein structure. As a general trend, the more a cation was kosmotropic (e.g., presenting a high B coefficient), the larger the resulting modifications were. The ability of these enzymes to bind the substrates was studied by fluorescence quenching in the presence of nicotinamide adenine dinucleotide (NAD + ) and azide. The dissociation constant for NAD + was only slightly affected by the grafting of the cations, however, the quenching efficiency was reduced. Azide binding was more affected by the cations. In the presence of 30 % (v/v) [MMIm][Me 2 PO 4 ], the catalytic efficiency of the wild‐type enzyme was reduced by 2.8 fold. In comparison, the catalytic efficiency of the modified FDH was preserved in these conditions and even improved after modification by hydroxypropyl imidazolium. The grafting of the chaotropic cations prevented the unfolding of the FDH due to [MMIm][Me 2 PO 4 ].