Molecular Basis of Aqueous-like Activity of Lipase Treated with Glucose-Headed Surfactant in Organic Solvent.

Lipases are useful as catalysts, particularly for the kinetic resolution of racemic alcohols and esters. However, their industrial applications are limited by their poor activities in organic media. We recently found that a lipoprotein lipase from Burkholderia species displays dramatically enhanced activity in organic solvent if the protein is coated with glucose-headed surfactant (GHS). Here we investigate the molecular basis of this enhanced enzymatic activity in organic solvent by performing molecular dynamics simulations on Burkholderia cepacia lipase as a model enzyme. Our simulation results indicate that the enhanced activity of lipase stems from a dual function of GHSs different in water and organic solvent. GHS molecules maintain the open conformation of lipase by providing lipid-like microenvironment surrounding the active site in water and stabilize its native active conformation by providing water-like microenvironment around the surface of the lipase in the organic solvent. Our data also suggest the role of organic cosolvent that can facilitate closed-to-open conformational changes during the freeze-drying process. The computational approach in this study lays its potential for guiding the design of more effective surfactant molecules to improve the activity of lipases in organic solvent.

Kinetic and dynamic kinetic resolution of secondary alcohols with ionic-surfactant-coated Burkholderia cepacia lipase: substrate scope and enantioselectivity.

Forty-four different secondary alcohols, which can be classified into several types (II-IX), were tested as the substrates of ionic surfactant-coated Burkholderia cepacia lipase (ISCBCL) to see its substrate scope and enantioselectivity in kinetic and dynamic kinetic resolution (KR and DKR). They include 6 boron-containing alcohols, 24 chiral propargyl alcohols, and 14 diarylmethanols. The results from the studies on KR indicate that ISCBCL accepted most of them with high enantioselectivity at ambient temperature and with useful to high enantioselectivity at elevated temperatures. In particular, ISCBCL displayed high enantioselectivity toward sterically demanding secondary alcohols (types VIII and IX) which have two bulky substituents at the hydroxymethine center. DKR reactions were performed by the combination of ISCBCL with a ruthenium-based racemization catalyst at 25-60 °C. Forty-one secondary alcohols were tested for DKR. About half of them were transformed into their acetates of high enantiopurity (>90% ee) with good yields (>80%). It is concluded that ISCBCL appears to be a superb enzyme for the KR and DKR of secondary alcohols.