title: High transesterification activities of immobilized proteases in new ether-functionalized ionic liquids.
abstract: Three new ether-functionalized hydrophobic ionic liquids (ILs) were synthesized. Two proteases (subtilisin and alpha-chymotrypsin both covalently immobilized on chitosan) exhibited high synthetic activity (1-3 micromol/min x g) and selectivity (>97-99%, esterification over hydrolysis) in these ILs containing 10-15% (v/v) water during the transesterification of N-acetyl-L-phenylalanine ethyl ester with 1-propanol. However, the same reaction in t-butanol or [BMIM][Tf(2)N], with water contents higher than 2% (v/v) yielded low synthetic activities (0.2-1 micromol/min g in t-butanol) and/or poor selectivity (<40%). The high synthetic activities of proteases in ether-functionalized ILs at high water contents are explained by two reasons: (1) the hydrogen-bond donors in ILs (R(1)-O-R(2)) and chitosan (-OH) controlling the thermodynamic water activity of the reaction system, and (2) the protective role of the ether chain in reducing the cation-protein interaction.
authors.affiliation: Chemistry Program, Savannah State University, Savannah, GA 31404, USA. huazhao98@gmail.com
authors.forename: Hua
authors.initials: H
authors.lastname: Zhao
authors.forename: Zhiyan
authors.initials: Z
authors.lastname: Song
authors.forename: Olarongbe
authors.initials: O
authors.lastname: Olubajo
mesh_terms: D002918:Chymotrypsin / Q000737:chemistry; D004800:Enzymes, Immobilized / Q000378:metabolism*; D004951:Esterification; D004987:Ethers / Q000737:chemistry*; D057927:Hydrophobic and Hydrophilic Interactions; D052578:Ionic Liquids / Q000737:chemistry*; D015394:Molecular Structure; D010447:Peptide Hydrolases / Q000378:metabolism*; D020860:Subtilisin / Q000737:chemistry; D014783:Viscosity
chemical_list: D004800:Enzymes, Immobilized; D004987:Ethers; D052578:Ionic Liquids; D010447:Peptide Hydrolases; D002918:Chymotrypsin; C117608:alpha-chymotrypsin; D020860:Subtilisin