Peculiar features of four enzymes of the CaLA superfamily in aqueous media: Differences in substrate specificities and abilities to catalyze alcoholysis

Enzymatic transesterification of urethane-bond containing ester

Here we demonstrate the feasibility and successful application of enzymes in polyurethane network synthesis as well as occurring hurdles that have to be addressed when using urethanes synthesis substrates. The enzymatic transesterification of an urethane-bond containing monofunctional ester and a model alcohol carbitol using lipases is discussed. The reaction is optimized in terms of transesterification time and temperature, the reaction solvent, the possibility of a cosolvent and the alcohol amount, the used transesterification environment, and the biocatalyst. Enzymatic cross-linking of polyurethanes can open up a pool of new possibilities for cross-linking and related polyurethane network properties due to the enzymes high enantio-, stereo-, and regioselectivity and broad substrate spectrum.

Application of lipase immobilized on a hydrophobic support for the synthesis of aromatic esters

The present study aimed at preparing three biocatalysts via physical adsorption of lipases from Candida rugosa (CRL), Mucor javanicus, and Candida sp. on a hydrophobic and mesoporous support (Diaion HP-20). These biocatalysts were later applied to the synthesis of aromatic esters of apple peel and citrus (hexyl butyrate), apple and rose (geranyl butyrate), and apricot and pineapple (propyl butyrate). Scanning electron microscopy and gel electrophoresis confirmed a selective adsorption of lipases on Diaion, thus endorsing simultaneous immobilization and purification. Gibbs free energy (∆G) evinced the spontaneity of the process (-17.9 kJ/mol ≤ ∆G ≤ -5.1 kJ/mol). Maximum immobilized protein concentration of 30 mg/g support by CRL. This biocatalyst was the most active in olive oil hydrolysis (hydrolytic activity of 126.0 ± 2.0 U/g) and in the synthesis of aromatic esters. Maximum conversion yield of 89.1% was attained after 150 Min for the synthesis of hexyl butyrate, followed by the synthesis of geranyl butyrate (87.3% after 240 Min) and propyl butyrate (80.0% after 150 Min). CRL immobilized on Diaion retained around 93% of its original activity after six consecutive cycles of 150 Min for the synthesis of hexyl butyrate.

Tailoring chemoenzymatic oxidation via in situ peracids

Epoxidation chemistry often suffers from the challenging handling of peracids and thus requires in situ preparation. Here, we describe a two-phase enzymatic system that allows the effective generation of peracids and directly translate their activity to the epoxidation of olefins. We demonstrate the approach by application to lipid and olefin epoxidation as well as sulfide oxidation. These methods offer useful applications to synthetic modifications and scalable green processes.

Inhibition of CpLIP2 Lipase Hydrolytic Activity by Four Flavonols (Galangin, Kaempferol, Quercetin, Myricetin) Compared to Orlistat and Their Binding Mechanisms Studied by Quenching of Fluorescence

The inhibition of recombinant CpLIP2 lipase/acyltransferase from Candida parapsiolosis was considered a key model for novel antifungal drug discovery and a potential therapeutic target for candidiasis. Lipases have identified recently as potent virulence factors in C. parapsilosis and some other yeasts. The inhibition effects of orlistat and four flavonols (galangin, kaempferol, quercetin and myricetin) characterized by an increasing degree of hydroxylation in B-ring, were investigated using ethyl oleate hydrolysis as the model reaction. Orlistat and kaempferol (14 µM) strongly inhibited CpLIP2 catalytic activity within 1 min of pre-incubation, by 90% and 80%, respectively. The relative potency of flavonols as inhibitors was: kaempferol > quercetin > myricetin > galangin. The results suggested that orlistat bound to the catalytic site while kaempferol interacted with W294 on the protein lid. A static mechanism of interactions between flavonols and CpLIP2 lipase was confirmed by fluorescence quenching analyses, indicating that the interactions were mainly driven by hydrophobic bonds and electrostatic forces. From the Lehrer equation, fractions of tryptophan accessibility to the quencher were evaluated, and a relationship with the calculated number of binding sites was suggested.

What makes a lipase a valuable acyltransferase in water abundant medium?

The necessity to develop more eco-friendly processes in oleochemistry has recently led to a renewed consideration of lipases exhibiting high acyltransferase activity in hydrated media.

Biodiesel production from crude jatropha oil catalyzed by immobilized lipase/acyltransferase from Candida parapsilosis in aqueous medium

The lipase/acyltransferase from Candida parapsilosis (CpLIP2) immobilized on two synthetic resins (Accurel MP 1000 and Lewatit VP OC 1600) was used as catalyst for the production of biodiesel (fatty acid methyl esters, FAME) by transesterification of jatropha oil with methanol, in a lipid/aqueous system. The oil was dispersed in a buffer solution (pH 6.5) containing methanol in excess (2M in the biphasic system; molar ratio methanol/acyl chains 2:1). Transesterification was carried out at 30°C, under magnetic stirring, using 10% (w/w) of immobilized enzyme in relation to oil. The maximum FAME yields were attained after 8h reaction time: 80.5% and 93.8%, when CpLIP2 immobilized on Accurel MP 1000 or on Lewatit VP OC 1600 were used, respectively. CpLIP2 on both Accurel MP 1000 and Lewatit VP OC 1600 showed high operational stability along 5 consecutive 8h batches.

One-pot biocatalytic amine transaminase/acyl transferase cascade for aqueous formation of amides from aldehydes or ketones

A novel biocatalytic amine transaminase/acyl transferase cascade for the formation of amides in aqueous solution has been developed.

The 3D model of the lipase/acyltransferase from Candida parapsilosis, a tool for the elucidation of structural determinants in CAL-A lipase superfamily

Because lipids are hydrophobic, the development of efficient bioconversions in aqueous media free of organic solvents is particularly challenging for green oleochemistry. Within this aim, enzymes exhibiting various abilities to catalyze acyltransfer reaction in water/lipid systems have been identified. Among these, CpLIP2 from Candida parapsilosis has been characterized as a lipase/acyltransferase, able to catalyze acyltransfer reactions preferentially to hydrolysis in the presence of particularly low acyl acceptor concentration and high thermodynamic activity of water (aw>0.9). Lipase/acyltransferases are thus of great interest, being able to produce new esters at concentrations above the thermodynamic equilibrium of hydrolysis/esterification with limited to no release of free fatty acids. Here, we present a 3D model of CpLIP2 based on homologies with crystallographic structures of Pseudozyma antarctica lipase A. Indeed, the two enzymes have 31% of identity in their primary sequence, yielding a same general structure, but different catalytic properties. The quality of the calculated CpLIP2 model was confirmed by several methods. Limited proteolysis confirmed the location of some loops at the surface of the protein 3D model. Directed mutagenesis also supported the structural model constructed on CAL-A template: the functional properties of various mutants were consistent with their structure-based putative involvement in the oxyanion hole, substrate specificity, acyltransfer or hydrolysis catalysis and structural stability. The CpLIP2 3D model, in comparison with CAL-A 3D structure, brings insights for the elucidation and improvement of the structural determinants involved in the exceptional acyltransferase properties of this promising biocatalyst and of homologous enzymes of the same family.

Homologous yeast lipases/acyltransferases exhibit remarkable cold-active properties

Lipases/acyltransferases catalyse acyltransfer to various nucleophiles preferentially to hydrolysis even in aqueous media with high thermodynamic activity of water (a w >0.9). Characterization of hydrolysis and acyltransfer activities in a large range of temperature (5 to 80 °C) of secreted recombinant homologous lipases of the Pseudozyma antarctica lipase A superfamily (CaLA) expressed in Pichia pastoris, enlighten the exceptional cold-activity of two remarkable lipases/acyltransferases: CpLIP2 from Candida parapsilosis and CtroL4 from Candida tropicalis. The activation energy of the reactions catalysed by CpLIP2 and CtroL4 was 18-23 kJ mol(-1) for hydrolysis and less than 15 kJ mol(-1) for transesterification between 5 and 35 °C, while it was respectively 43 and 47 kJ mol(-1) with the thermostable CaLA. A remarkable consequence is the high rate of the reactions catalysed by CpLIP2 and CtroL4 at very low temperatures, with CpLIP2 displaying at 5 °C 65 % of its alcoholysis activity and 45 % of its hydrolysis activity at 30 °C. These results suggest that, within the CaLA superfamily and its homologous subgroups, common structural determinants might allow both acyltransfer and cold-active properties. Such biocatalysts are of great interest for the efficient synthesis or functionalization of temperature-sensitive lipid derivatives, or more generally to lessen the environmental impact of biocatalytic processes.