title: Ionization basis for activation of enzymes soluble in ionic liquids.
abstract: BACKGROUND
  The complex interactions between electrolytes and proteins have been studied for more than a century. However, understanding is not yet complete and does not provide a basis for predicting the activity of enzymes in ionic media. The use of ionic liquids (ILs) as reaction medium has opened up new opportunities for better understanding of the mechanism of enzymatic catalysis. Although a number of properties of ILs have been correlated with enzyme function, these relationships are not completely understood at a molecular level.
  
  
  METHODS
  We propose that ILs must be able to promote ionization of protein ionizable groups in order to dissolve active enzymes. The biocompatible IL need to possess a functional group with large donor number and acceptor number in both cationic and anionic units, each of which is based on a high dielectric constant lead structure. We designed and synthesized two series of ILs and determined their ionizing-dissociating abilities and activities of lipases soluble in these new ILs.
  
  
  RESULTS
  The results showed that the ionizing-dissociating abilities of ILs paralleled the catalytic activity trend of lipases dissolved in the ILs. The activities of lipases soluble in the newly designed ILs were comparable to those in water.
  
  
  CONCLUSIONS
  We can conclude that ionizing-dissociating abilities of an IL can be used as a basis for predicting the activity of enzymes soluble in the IL. General significance Ionization basis for activation of enzymes gives a deeper understanding of the behavior of enzymes in non-aqueous media at a molecular level.
authors.affiliation: School of Bioengineering, Jimei University, Xiamen 361021, PR China; WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XW, UK.
authors.forename: Guangnan
authors.initials: G
authors.lastname: Ou
authors.affiliation: School of Bioengineering, Jimei University, Xiamen 361021, PR China.
authors.forename: Biyan
authors.initials: B
authors.lastname: He
authors.affiliation: WestCHEM, Department of Pure and Applied Chemistry, University of Strathclyde, Glasgow G1 1XW, UK.
authors.forename: Peter
authors.initials: P
authors.lastname: Halling
mesh_terms: D020001:1-Butanol / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D016956:Burkholderia cepacia / Q000201:enzymology*; D002087:Butyrates / Q000378:metabolism; D002175:Candida / Q000201:enzymology*; D002384:Catalysis; D002412:Cations; D004789:Enzyme Activation; D004951:Esterification; D005656:Fungal Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D052578:Ionic Liquids / Q000737:chemistry*; D008049:Lipase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D009211:Myoglobin / Q000737:chemistry; D011487:Protein Conformation; D012995:Solubility; D013329:Structure-Activity Relationship
chemical_list: D001426:Bacterial Proteins; D002087:Butyrates; D002412:Cations; D005656:Fungal Proteins; D052578:Ionic Liquids; D009211:Myoglobin; D020001:1-Butanol; D008049:Lipase; C045572:ethyl butyrate
keywords: Activation; Enzyme; Ionic liquid; Ionization