Lipases and (R)-oxynitrilases: useful tools in organic synthesis

Simple synthetic route to an enzyme-inspired transesterification catalyst

Self-assembling transesterification catalyst inspired by the catalytic triad.

Optimization of the Lipase-Catalyzed Selective Amidation of Phenylglycinol

Ceramides and their analogs have a regulatory effect on inflammatory cytokines expression. It was found that a kind of ceramides analog synthesized from phenylglycinol could inhibit the production of cytokine TNF-α. However, two active hydrogen groups are present in the phenylglycinol molecule. It is difficult to control the process without hydroxyl group protection to dominantly produce amide in the traditional chemical synthesis. A selective catalytic the amidation route of phenylglycinol by lipases was investigated in this research. The results indicated that the commercial immobilized lipase Novozym 435 has the best regio-selectivity on the amide group. Based on the experimental results and in silico simulation, it was found that the mechanism of specific N-acyl selectivity of lipase was not only from intramolecular migration and proton shuttle mechanism, but also from the special structure of active site of enzyme. The optimal reaction yield of aromatic amide compound in a solvent-free system with lipase loading of 15 wt% (to the weight of total substrate) reached 89.41 ± 2.8% with very few of byproducts detected (0.21 ± 0.1% ester and 0.64 ± 0.2% diacetylated compound). Compare to other reported works, this work have the advantages such as low enzyme loading, solvent free, and high N-acylation selectivity. Meanwhile, this Novozym 435 lipase based synthesis method has an excellent regio-selectivity on most kinds of amino alcohol compounds. Compared to the chemical method, the enzymatic synthesis exhibited high regio-selectivity, and conversion rates. The method could be a promising alternative strategy for the synthesis of aromatic alkanolamides.

Beauveria bassiana Lipase A expressed in Komagataella (Pichia) pastoris with potential for biodiesel catalysis

Lipases (EC 3.1.1.3) comprise a biotechnologically important group of enzymes because they are able to catalyze both hydrolysis and synthesis reactions, depending on the amount of water in the system. One of the most interesting applications of lipase is in the biofuel industry for biodiesel production by oil and ethanol (or methanol) transesterification. Entomopathogenic fungi, which are potential source of lipases, are still poorly explored in biotechnological processes. The present work reports the heterologous expression and biochemical characterization of a novel Beauveria bassiana lipase with potential for biodiesel production. The His-tagged B. bassiana lipase A (BbLA) was produced in Komagataella pastoris in buffered methanol medium (BMM) induced with 1% methanol at 30°C. Purified BbLA was activated with 0.05% Triton X-100 and presented optimum activity at pH 6.0 and 50°C. N-glycosylation of the recombinant BbLA accounts for 31.5% of its molecular weight. Circular dichroism and molecular modeling confirmed a structure composed of α-helix and β-sheet, similar to α/β hydrolases. Immobilized BbLA was able to promote transesterification reactions in fish oil, demonstrating potential for biodiesel production. BbLA was successfully produced in K. pastoris and shows potential use for biodiesel production by the ethanolysis reaction.

Lipase in aqueous-polar organic solvents: activity, structure, and stability

Studying alterations in biophysical and biochemical behavior of enzymes in the presence of organic solvents and the underlying cause(s) has important implications in biotechnology. We investigated the effects of aqueous solutions of polar organic solvents on ester hydrolytic activity, structure and stability of a lipase. Relative activity of the lipase monotonically decreased with increasing concentration of acetone, acetonitrile, and DMF but increased at lower concentrations (upto ~20% v/v) of dimethylsulfoxide, isopropanol, and methanol. None of the organic solvents caused any appreciable structural change as evident from circular dichorism and NMR studies, thus do not support any significant role of enzyme denaturation in activity change. Change in 2D [15N, 1H]-HSQC chemical shifts suggested that all the organic solvents preferentially localize to a hydrophobic patch in the active-site vicinity and no chemical shift perturbation was observed for residues present in protein's core. This suggests that activity alteration might be directly linked to change in active site environment only. All organic solvents decreased the apparent binding of substrate to the enzyme (increased Km ); however significantly enhanced the kcat . Melting temperature (Tm ) of lipase, measured by circular dichroism and differential scanning calorimetry, altered in all solvents, albeit to a variable extent. Interestingly, although the effect of all organic solvents on various properties on lipase is qualitatively similar, our study suggest that magnitudes of effects do not appear to follow bulk solvent properties like polarity and the solvent effects are apparently dictated by specific and local interactions of solvent molecule(s) with the protein.

Characterization of a novel lipase from Bacillus sp. isolated from tannery wastes

Kinetics of a lipase isolated from Bacillus sp. was studied. The enzyme showed maximum activity at pH 9 and temperature 60°C. The Michaelis constant (KM 0.31 mM) obtained from three different plots i.e., Lineweaver-Burk, Hanes-Wolf and Hofstee, was found to be lower than already reported lipases that confirmed higher affinity of the enzyme for its substrate p-NPL (p-nitrophenyl laurate). Vmax of the enzyme was found to be 7.6 µM/mL/min. Energy of activation calculated from Arrhenius plot was found to be 20.607 kJmol(-1). Activation enthalpy (ΔH*) had negative trend and the value for the hydrolysis of p-NPL by the enzyme at optimum temperature was -2.748 kJmol(-1). Activation entropy (ΔS*) and free energy of activation (ΔG*) of the enzyme were found to be 1.468 Jmol(-1)K(-1) and -3.237 kJmol(-1), respectively at optimum temperature. Low value of Q10 (0.04788) shows high catalytic activity of the enzyme. Mn(2+), Fe(2+) and Mg(2+) enhanced the lipase activity whereas Cu(2+), Na(+) and Co(2+) inhibited the enzyme activity. However, the enzyme activity was not affected significantly by K(+) ions. EDTA and SDS also significantly inhibited the lipase activity. Activity of the enzyme was increased in n-hexane while decreased with increase in concentration of acetone, chloroform, ethanol and isopropanol.

Enzymatic chemoselective synthesis of secondary-amide surfactant from N-methylethanol amine

Efficient selective synthesis of the secondary amide surfactant N-methyl lauroylethanolamide from methyl laurate and N-methylethanol amine by carrier-fixed Chirazyme L-2 (Candida antarctica) using a kinetic strategy has been demonstrated. When different solvents were screened for product yields using Chirazyme L-2, acetonitrile was found to be optimal. The rate of the reaction increased sharply by increasing the molar ratio of the reactants and the reaction temperature. When the reaction was performed at 50 degrees C for 36 h with 50 mmol ester and 100 mmol amine, the product was obtained in a 97.1% yield. With 50 mmol ester and 150 mmol amine, the highest yield (97.3%) was obtained after 16 h of incubation at 50 degrees C. It took only 5 h to get a yield of 95.8% at 60 degrees C using 50 mmol ester and 200 mmol amine. The enzyme activity in the amidation reaction mixture did not decrease notably even after six uses.

The molecular reaction vessels for a transesterification process created by molecular imprinting technique

A polymeric catalyst was synthesized by co-polymerizing 4(5)-vinylimidazole and itaconic acid with trimethylpropanol trimethacrylate micro spheres. The catalyst obtained catalysed the transesterification process between p-nitrophenyl acetate and hexanol with maximal initial velocity(nu(max)) of 4.73 +/- 0.47 microM min(-1) mg(-1), and turnover rate (k(cat)) of 8.67 min(-1). Using p-nitrophenyl acetate as template, molecular imprinting process enhanced the nu(max) of the polymeric catalyst 3-fold. Each imprinted site can be considered as a single molecular reaction vessel, and achieved a k(cat) of 169 min(-1) towards the conversion of p-nitrophenyl acetate in hexanol.

Kinetic resolution of ibuprofen catalyzed byCandida rugosa lipase in ionic liquids

Candida rugosa lipase-catalyzed esterification of ibuprofen with 1-propanol was conducted in seven ionic liquids and the results were compared with those in isooctane. Although the enzyme showed comparable or higher activity in some ionic liquids compared to that in isooctane, only in the case of [BMIM]PF6 was the enantioselectivity (E = 24.1) almost twice that (E = 13.0) of isooctane. In another six ionic liquids the enzyme enantioselectivity was much poorer (E = 1.1-6.4). At the same conversion of 30%, E of [BMIM]PF6 is more than triple that of isooctane. The lipase stability in [BMIM]PF6 was improved by 25% of that in isooctane. It was concluded that [BMIM]PF6 could be applied to substitute the conventional organic solvent (isooctane) in the esterification of ibuprofen.

Biocatalytic conversion of epoxides

Epoxides are attractive intermediates for producing chiral compounds. Important biocatalytic reactions involving epoxides include epoxide hydrolase mediated kinetic resolution, leading to the formation of diols and enantiopure remaining substrates, and enantioconvergent enzymatic hydrolysis, which gives high yields of a single enantiomer from racemic mixtures. Epoxides can also be converted by non-hydrolytic enantioselective ring opening, using alternative anionic nucleophiles; these reactions can be catalysed by haloalcohol dehalogenases. The differences in scope of these enzymatic conversions is related to their different catalytic mechanisms, which involve, respectively, covalent catalysis with an aspartate carboxylate as the nucleophile and non-covalent catalysis with a tyrosine that acts as a general acid-base. The emerging new possibilities for enantioselective biocatalytic conversion of epoxides suggests that their importance in green chemistry will grow.