title: Importance of the ionic nature of ionic liquids in affecting enzyme performance.
abstract: The activity and stability of mushroom tyrosinase were studied in ionic liquid (IL)-containing aqueous systems. The effect of three ILs ([BMIm][PF(6)], [BMIm][BF(4)]), and [BMIm][MeSO(4)], where [BMIm] = 1-butyl-3-methylimidazolium) and their inorganic salts (KMeSO(4), KPF(6), and NaBF(4)) on the enzyme performance was investigated by comparing the kinetic (such as K(m), V(max), optimal pH and temperature, and activation energy) and thermostability parameters (including half-lives, deactivation constants, activation energies for enzyme deactivation, DeltaG*, DeltaH*, and DeltaS*) of the enzyme in the absence and presence of the ILs and their anions. Both the three ILs and their inorganic salts were able to trigger enzyme activation. The enzyme could be stabilized by addition of KMeSO(4) and NaBF(4) but destabilized by the presence of all the three ILs. The substrate selectivity of the enzyme was unchanged. The effect of ILs on enzyme performance can be largely attributed to their ionic nature via interaction with the enzyme structure, the substrate, and the water molecules associated with the enzyme, depending on their kosmotropocity, nucleophilicity, and H-bond basicity. The different influences brought from the ILs and their associated ions indicate the cooperative functioning of both cation and anion of the IL in affecting the enzyme performance.
authors.affiliation: College of Life Sciences, Shenzhen University, Shenzhen, Guangdong 518060, China.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Yang
authors.forename: Ya-Jun
authors.initials: YJ
authors.lastname: Yue
authors.forename: Wen-Chao
authors.initials: WC
authors.lastname: Huang
authors.forename: Xiao-Ma
authors.initials: XM
authors.lastname: Zhuang
authors.forename: Zheng-Tao
authors.initials: ZT
authors.lastname: Chen
authors.forename: Miao
authors.initials: M
authors.lastname: Xing
mesh_terms: D000363:Agaricales / Q000201:enzymology*; D000838:Anions; D055162:Biocatalysis / Q000187:drug effects; D002021:Buffers; D004789:Enzyme Activation / Q000187:drug effects; D004795:Enzyme Stability / Q000187:drug effects; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D052578:Ionic Liquids / Q000737:chemistry / Q000494:pharmacology*; D007700:Kinetics; D014442:Monophenol Monooxygenase / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D012492:Salts / Q000494:pharmacology; D012996:Solutions; D013379:Substrate Specificity / Q000187:drug effects; D013696:Temperature
chemical_list: D000838:Anions; D002021:Buffers; D052578:Ionic Liquids; D012492:Salts; D012996:Solutions; D014442:Monophenol Monooxygenase