Polar organic solvents such as methanol or N-methylformamide inactivate lipases. Although ionic liquids such as 3-alkyl-1-methylimidazolium tetrafluoroborates have polarities similar to these polar organic solvents, they do not inactivate lipases. To get reliable lipase-catalyzed reactions in ionic liquids, we modified their preparation by adding a wash with aqueous sodium carbonate. Lipase-catalyzed reactions that previously did not occur in untreated ionic liquids now occur at rates comparable to those in nonpolar organic solvents such as toluene. Acetylation of 1-phenylethanol catalyzed by lipase from Pseudomonas cepacia (PCL) was as fast and as enantioselective in ionic liquids as in toluene. Ionic liquids permit reactions in a more polar solvent than previously possible. Acetylation of glucose catalyzed by lipase B from Candida antarctica (CAL-B) was more regioselective in ionic liquids because glucose is up to one hundred times more soluble in ionic liquids. Acetylation of insoluble glucose in organic solvents yielded the more soluble 6-O-acetyl glucose, which underwent further acetylation to give 3,6-O-diacetyl glucose (2-3:1 mixture). However, acetylation of glucose in ionic liquids yielded only 6-O-acetyl glucose (>13:1 and up to >50:1).

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Bioconjugation of functional proteins onto metal-organic frameworks (MOFs) has been achieved using activation of pendent linking groups of the organic linkers on the surface of MOFs. Fluorescent microscopy revealed successful conjugation of an enhanced fluorescent protein onto MOFs. In addition, Candida-antarctica-lipase-B-conjugated MOFs showed no loss of enantioselectivity and activity in transesterification of (±)-1-phenylethanol.

The structure of PFE, an aryl esterase from Pseudomonas fluorescens, has been solved to a resolution of 1.8 A by X-ray diffraction and shows a characteristic alpha/beta-hydrolase fold. In addition to catalyzing the hydrolysis of esters in vitro, PFE also shows low bromoperoxidase activity. PFE shows highest structural similarity, including the active-site environment, to a family of non-heme bacterial haloperoxidases, with an r.m.s. deviation in 271 C(alpha) atoms between PFE and its five closest structural neighbors averaging 0.8 A. PFE has far less similarity (r.m.s. deviation in 218 C(alpha) atoms of 5.0 A) to P. fluorescens carboxyl esterase. PFE favors activated esters with small acyl groups, such as phenyl acetate. The X-ray structure of PFE reveals a significantly occluded active site. In addition, several residues, including Trp28 and Met95, limit the size of the acyl-binding pocket, explaining its preference for small acyl groups.