In this work, we explored the activation of a lipoprotein lipase from Burkholderia sp. by surfactants, sugars, and sugar–surfactant combinations for enhancing its activity in organic solvent. The lipase was most strongly activated by the combination of dextrin and anionic surfactant 1. As a result, its turnover frequency in anhydrous toluene reached 420 s–1, which was comparable to its aqueous counterpart. It was also found that a glucosamine-headed surfactant 8 as a molecular mimic of the dextrin-1 combination enhanced the turnover frequency of LPL to the aqueous level. As a rationale for such a high turnover frequency of lipoprotein lipase in anhydrous organic solvent, we speculate that the dextrin-1 couple or its mimic 8 could provide an efficient water-mimicking hydrogen bonding network around the enzyme in addition to the contribution as the oil surrogate, thus leading to a large increase of active enzyme molecules.

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.

We explored the kinetic resolution of 31 different diarylmethanols with an activated lipoprotein lipase (LPL-D1) which was about 3000-fold more active than its native counterpart in organic solvent. Most of the substrates tested were accepted by LPL-D1 with good to high enantioselectivity in the kinetic resolution. Next, we explored the dynamic kinetic resolutions (DKRs) of these substrates (24 out of 31) using LPL-D1 and a ruthenium-based racemization catalyst in combination, which provided satisfactory yields (71-96%) and high enantiopurities (90-99% ee). As an illustrative example for the synthetic applications of the DKR procedure, we synthesized L-cloperastine, an antitussive drug, from phenyl-(p-trimethylsilylphenyl)methanol via DKR.

No abstract

No abstract

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.

Two benzoate surfactants were synthesized and examined as the additives for enhancing the activity of a lipoprotein lipase from Burkholderia species (BSLPL) in organic solvent. It was found that the benzoate surfactants enhanced the turnover number (k cat ) by four orders of magnitude and the catalytic efficiency (k cat /K m ) by three orders of magnitude. These results strongly suggest that the favorable interaction between the aromatic rings of surfactant tails and the hydrophobic residues around the active site of enzyme may help BSLPL maintain highly active open conformation in organic solvent.

The structural effect of benzoate surfactant tails on the activity of lipoprotein lipase from Burkholderia species.