A model for interfacial activation in lipases from the structure of a fungal lipase-inhibitor complex

Exploring the influence of phospholipid monolayer conformation and environmental conditions on the interfacial binding of Gibberella Zeae lipase

The involvement of different parameters on Gibberella zeae lipase (GZEL) membrane binding were characterized by using monomolecular film technology and circular dichroism spectroscopy. Among four kinds of phospholipid monolayers, 1,2‑dimyristoyl‑sn‑glycero‑3‑phosphoethanolamine have the highest maximum insertion pressure (MIP) value. Comparing the GZEL adsorption to phosphatidylcholine monolayers with different acyl chains in sn-1 and sn-2 positions, the higher MIP values were found for 1,2‑dilauroyl‑sn‑glycero‑3‑phosphocholine. Significantly improvement between 1,2‑dioleoyl‑sn‑glycero‑3‑phosphocholine and 1,2‑distearoyl‑sn‑glycero‑3‑phosphocholine suggested that the presence of fatty acid unsaturation may affect protein adsorption by changing the chemical structure in each phospholipid. The MIP value was shown higher (48.6 mN m^-1) at pH 5 and pH 6 (47.5 ± 1.9 mN m^-1) but decreased significantly (34.2 mN m^-1) at pH 9. This may indicate that the proportion of helices in the protein decreases with the alteration of the catalytic center, thus affecting the binding of the protein to its substrate. The MIP values obviously decreased with increasing salt ion concentration, suggesting that excessive salt ion concentration may destabilize the secondary and tertiary structures of the protein, thereby affecting the characteristics of its adsorption at the interfaces. Present studies improve our understanding on the protein-membrane interaction of this enzyme.

Novel Inhibitory Function of the Rhizomucor miehei Lipase Propeptide and Three-Dimensional Structures of Its Complexes with the Enzyme

Many proteins are synthesized as precursors, with propeptides playing a variety of roles such as assisting in folding or preventing them from being active within the cell. While the precise role of the propeptide in fungal lipases is not completely understood, it was previously reported that mutations in the propeptide region of the Rhizomucor miehei lipase have an influence on the activity of the mature enzyme, stressing the importance of the amino acid composition of this region. We here report two structures of this enzyme in complex with its propeptide, which suggests that the latter plays a role in the correct maturation of the enzyme. Most importantly, we demonstrate that the propeptide shows inhibition of lipase activity in standard lipase assays and propose that an important role of the propeptide is to ensure that the enzyme is not active during its expression pathway in the original host.

Carboxypeptidase Y activity and maintenance is modulated by a large helical structure

Yeast carboxypeptidase Y (CPY) is a serine protease with broad substrate specificity. Structurally, CPY belongs to the α/β hydrolase fold family and contains characteristic large helices, termed the V‐shape helix, above the active site cavity. Four intramolecular disulfide bonds are located in and around the V‐shape helix. In this study, mutant CPYs were constructed in which one of these disulfide bonds was disrupted. Mutants lacking the C193–C207 bond located at the beginning of the V‐shape helix aggregated easily, while mutants lacking the C262–C268 bond located at the end of the V‐shape helix displayed decreased hydrolytic activity. The results indicate that the V‐shape helix is involved in CPY catalysis and in maintenance of its conformation.

Soluble expression of mature Rhizopus chinensis lipase in Escherichia coli and enhancement of its ester synthesis activity

The production of membrane-associated lipase from Rhizopus chinensis (RCL), which has a high ester synthesis activity and important potential applications, is difficult in heterologous expression system such as Escherichia coli and often leads to the formation of inclusion bodies. Here, we describe the soluble expression of mature RCL (mRCL) using maltose-binding protein (MBP) as a solubility-enhancing tag in the E. coli system. Although the MBP-mRCL fusion protein was soluble, mRCL was insoluble after removal of the MBP tag in E. coli BL21 (DE3). Using E. coli BL21 trxB (DE3) as an expression host, soluble mRCL was obtained and expression conditions were optimized. Furthermore, the ester synthesis activity of soluble mRCL was increased by detergent treatment and was found to be 3.5 and 1.5 times higher than those of the untreated enzyme and naturally occurring enzyme, respectively. Overall, this study provides a potential approach for producing active and soluble forms of eukaryotic lipases in a heterologous E. coli expression system.

Functional diversity of glycerolipid acylhydrolases in plant metabolism and physiology

Most current knowledge about plant lipid metabolism has focused on the biosynthesis of lipids and their transport between different organelles. However, lipid composition changes during development and in response to environmental cues often go beyond adjustments of lipid biosynthesis. When lipids have to be removed to adjust the extent of membranes during down regulation of photosynthesis, or lipid composition has to be adjusted to alter the biophysical properties of membranes, or lipid derived chemical signals have to be produced, lipid-degrading enzymes come into play. This review focuses on glycerolipid acylhydrolases that remove acyl groups from glycerolipids and will highlight their roles in lipid remodeling and lipid-derived signal generation. One emerging theme is that these enzymes are involved in the dynamic movement of acyl groups through different lipid pools, for example from polar membrane lipids to neutral lipids sequestered in lipid droplets during de novo triacylglycerol synthesis. Another example of acyl group sequestration in the form of triacylglycerols in lipid droplets is membrane lipid remodeling in response to abiotic stresses. Fatty acids released for membrane lipids can also give rise to potent signaling molecules and acylhydrolases are therefore often the first step in initiating the formation of these lipid signals.

Tailoring a robust and recyclable nanobiocatalyst by immobilization of Pseudomonas fluorescens lipase on carbon nanofiber and its application in synthesis of enantiopure carboetomidate analogue

Pseudomonas fluorescens lipase (PFL) was covalently immobilized on carbon nanofiber (CNF) using 1‑ethyl‑3‑[3‑dimethylaminopropyl] carbodiimide (EDC)/N‑hydroxysuccinimide (NHS). Surface functionalization of carbon nanofiber augments dispersibility as well as efficiency of covalent immobilization. Crucial parameters for immobilization such as pH, enzyme-support ratio, reaction time and mixing rate were optimized using one factor at a time (OFAT) approach. The nanobiocatalyst prepared under optimized conditions demonstrated a ten-fold increase in enzyme activity and the advantage of high thermal stability (up to 85 °C) along with 10 cycles of reusability. Subsequently practical application of the nanobiocatalyst was explored in the kinetic resolution of racemic 1‑phenylethanol into (S)‑1‑phenylethanol [C = 49.1%, ee_p = 99.5%, ee_s = 98.5% and E value = 151.4] followed by Mitsunobu reaction with a substituted pyrrole, giving an enantiopure (R)-carboetomidate analogue (yield = 83%).

Accelerated CO₂ Hydration with Thermostable Sulfurihydrogenibium azorense Carbonic Anhydrase-Chitin Binding Domain Fusion Protein Immobilised on Chitin Support

Carbonic anhydrases (CAs) represent a group of enzymes that catalyse important reactions of carbon dioxide hydration and dehydration, a reaction crucial to many biological processes and environmental biotechnology. In this study we successfully constructed a thermostable fusion enzyme composed of the Sulfurihydrogenibium azorense carbonic anhydrase (Saz_CA), the fastest CA discovered to date, and the chitin binding domain (ChBD) of chitinase from Bacillus circulans. Introduction of ChBD to the Saz_CA had no major impact on the effect of ions or inhibitors on the enzymatic activity. The fusion protein exhibited no negative effects up to 60 °C, whilst the fusion partner appears to protect the enzyme from negative effects of magnesium. The prepared biocatalyst appears to be thermally activated at 60 °C and could be partially purified with heat treatment. Immobilisation attempts on different kinds of chitin-based support results have shown that the fusion enzyme preferentially binds to a cheap, untreated chitin with a large crystallinity index over more processed forms of chitin. It suggests significant potential economic benefits for large-scale deployment of immobilised CA technologies such as CO₂ utilisation or mineralisation.

Pancreatic lipase inhibitory activity of selected pharmaceutical agents

Twenty-five structurally diverse compounds have been tested in vitro for their pancreatic lipase (PL) inhibitory activity. Despite the diversity of tested compounds, the relationship comprising structural attributes of the compounds could be established to correlate with the observed inhibitory activity. Compounds that exerted inhibitory action through surface activity were of different profile from the rest of compounds. When co-incubated with orlistat (OsT), important synergistic effects for some compounds (orphenadrine, gliclazide, cefuroxime and sulfacetamide) were revealed, while antagonistic effects were demonstrated for others (camphor sulfonic acid and dinitro salicylic acid). Docking studies for the most active molecules were performed and molecular interaction forces with the PL active site were identified. The results suggested co-binding of OsT along with the other inhibitor in the binding site in cases of synergistic effect but not in the case of antagonistic effect. These results were additionally supported by affinity capillary electrophoresis. In conclusion, synergistic lipase inhibitory activity between OsT and some other pharmaceutical compounds was demonstrated for the first time, which might help improve the pharmacological effect of OsT.

A Thermostable Monoacylglycerol Lipase from Marine Geobacillus sp. 12AMOR1: Biochemical Characterization and Mutagenesis Study

Lipases with unique substrate specificity are highly desired in biotechnological applications. In this study, a putative marine Geobacillus sp. monoacylglycerol lipase (GMGL) encoded gene was identified by a genomic mining strategy. The gene was expressed in Escherichia coli as a His-tag fusion protein and purified by affinity chromatography with a yield of 264 mg per liter fermentation broth. The recombinant GMGL shows the highest hydrolysis activity at 60 °C and pH 8.0, and the half-life was 60 min at 70 °C. The GMGL is active on monoacylglycerol (MAG) substrate but not diacylglycerol (DAG) or triacylglycerol (TAG), and produces MAG as the single product in the esterification reaction. Modeling structure analysis showed that the catalytic triad is formed by Ser97, Asp196 and His226, and the flexible cap region is constituted by residues from Ala120 to Thr160. A mutagenesis study on Leu142, Ile145 and Ile170 located in the substrate binding tunnel revealed that these residues were related with its substrate specificity. The k_cat/K_m value toward the pNP-C6 substrate in mutants Leu142Ala, Ile145Ala and Ile170Phe increased to 2.3-, 1.4- and 2.2-fold as compared to that of the wild type, respectively.

Novozym 435: the “perfect” lipase immobilized biocatalyst?

Novozym 435 (N435) is a commercially available immobilized lipase produced by Novozymes with its advantages and drawbacks.

Structure of the lipoprotein lipase-GPIHBP1 complex that mediates plasma triglyceride hydrolysis

Lipoprotein lipase (LPL) is responsible for the intravascular processing of triglyceride-rich lipoproteins. The LPL within capillaries is bound to GPIHBP1, an endothelial cell protein with a three-fingered LU domain and an N-terminal intrinsically disordered acidic domain. Loss-of-function mutations in LPL or GPIHBP1 cause severe hypertriglyceridemia (chylomicronemia), but structures for LPL and GPIHBP1 have remained elusive. Inspired by our recent discovery that GPIHBP1's acidic domain preserves LPL structure and activity, we crystallized an LPL-GPIHBP1 complex and solved its structure. GPIHBP1's LU domain binds to LPL's C-terminal domain, largely by hydrophobic interactions. Analysis of electrostatic surfaces revealed that LPL contains a large basic patch spanning its N- and C-terminal domains. GPIHBP1's acidic domain was not defined in the electron density map but was positioned to interact with LPL's large basic patch, providing a likely explanation for how GPIHBP1 stabilizes LPL. The LPL-GPIHBP1 structure provides insights into mutations causing chylomicronemia.

Synthesis of functional ionic liquid modified magnetic chitosan nanoparticles for porcine pancreatic lipase immobilization

We developed magnetic chitosan nanoparticles (CS‑Fe₃O₄) with mean diameter of 15-20 nm. Subsequently, these inorganic-organic composite nanoparticles were modified using an imidazole-based functional ionic liquid (IL). The prepared support (IL‑CS‑Fe₃O₄), which was used to immobilize porcine pancreatic lipase (PPL), was characterized using Fourier transform infrared (FTIR) spectroscopy, vibrating sample magnetometry (VSM), thermogravimetry (TG), transmission electron microscopy (TEM) and X-ray diffraction (XRD). Circular dichroism (CD) was used to analyze the secondary structure of immobilized PPL. The immobilized PPL (PPL‑IL‑CS‑Fe₃O₄) exhibited 1.93-fold higher specific activity than PPL‑CS-Fe₃O₄ when triacetin was used as the substrate, and showed 95 mg/g of lipase immobilization capacity and 382% of activity recovery. The residual activity of PPL‑IL‑CS‑Fe₃O₄ was above 60% of the initial activity after incubation at 50 °C for 6 h, as was higher than that of PPL‑CS‑Fe₃O₄ which showed 40% of the initial activity. In addition, PPL‑IL‑CS‑Fe₃O₄ retained 84.6% of the initial activity after 10 cycles, whereas PPL‑CS‑Fe₃O₄ retained only 75.5% activity. Furthermore, the kinetic parameters, apparent K_m and V_max of PPL‑IL‑CS‑Fe₃O₄ were 2.51 mg/mL and 1.395 U/mg respectively, these results indicated that the immobilized PPL had better affinity towards the substrate, especially when the nanoparticles were modified by functional IL. Besides, the magnetic chitosan nanoparticles loaded with PPL were easily recovered. A novel, efficient, and practical method for enzyme immobilization was developed.

Immobilization on octyl-agarose beads and some catalytic features of commercial preparations of lipase a from Candida antarctica (Novocor ADL): Comparison with immobilized lipase B from Candida antarctica

Lipase A from Candida antarctica (CALA, commercialized as Novocor ADL) was immobilized on octyl-agarose, which is a very useful support for lipase immobilization, and coated with polyethylenimine to improve the stability. The performance was compared to that of the form B of the enzyme (CALB) immobilized on the same support, as both enzymes are among the most popular ones used in biocatalysis. CALA immobilization produced a significant increase in enzyme activity vs. p-nitrophenyl butyrate (pNPB) (by a factor of seven), and the coating with PEI did not have a significant effect on enzyme activity. CALB reduced its activity slightly after enzyme immobilization. Octyl-CALA was less stable than octyl-CALB at pH 9 and more stable at pH 5 and, more clearly, at pH 7. PEI coating only increased octyl-CALA stability at pH 9. In organic solvents, CALB had much better stability in methanol and was similarly stable in acetonitrile or dioxane. In these systems, the PEI coating of octyl-CALA permitted some stabilization. While octyl-CALA was more active vs. pNPB, octyl-CALB was much more active vs. mandelic esters or triacetin. Thus, depending on the specific reaction and the conditions, CALA or CALB may offer different advantages and drawbacks. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2735, 2019.

Immobilization of Eversa Lipase on Octyl Agarose Beads and Preliminary Characterization of Stability and Activity Features

Eversa is an enzyme recently launched by Novozymes to be used in a free form as biocatalyst in biodiesel production. This paper shows for first time the immobilization of Eversa (a commercial lipase) on octyl and aminated agarose beads and the comparison of the enzyme properties to those of the most used lipase, the isoform B from Candida antarctica (CALB) immobilized on octyl agarose beads. Immobilization on octyl and aminated supports of Eversa has not had a significant effect on enzyme activity versus p-nitrophenyl butyrate (pNPB) under standard conditions (pH 7), but immobilization on octyl agarose beads greatly enhanced the stability of the enzyme under all studied conditions, much more than immobilization on aminated support. Octyl-Eversa was much more stable than octyl-CALB at pH 9, but it was less stable at pH 5. In the presence of 90% acetonitrile or dioxane, octyl-Eversa maintained the activity (even increased the activity) after 45 days of incubation in a similar way to octyl-CALB, but in 90% of methanol, results are much worse, and octyl-CALB became much more stable than Eversa. Coating with PEI has not a clear effect on octyl-Eversa stability, although it affected enzyme specificity and activity response to the changes in the pH. Eversa immobilized octyl supports was more active than CALB versus triacetin or pNPB, but much less active versus methyl mandelate esters. On the other hand, Eversa specificity and response to changes in the medium were greatly modulated by the immobilization protocol or by the coating of the immobilized enzyme with PEI. Thus, Eversa may be a promising biocatalyst for many processes different to the biodiesel production and its properties may be greatly improved following a suitable immobilization protocol, and in some cases is more stable and active than CALB.

High-level expression and characterization of a stereoselective lipase from Aspergillus oryzae in Pichia pastoris

Pichia pastoris expression is a mature and efficient eukaryotic expression system. In this work, Aspergillus oryzae lipase (AOL, with the molecular mass of 28 kDa), which can perform highly stereoselective hydrolysis of (R, S)-methyl 2-(4-hydroxyphenoxy) propanoate, was expressed in P. pastoris X-33. The specific activity of AOL was 432 U/mg, which was obtained by fed-batch cultivation in a 5 L bioreactor using a methanol feeding strategy. After fermentation, the supernatant was concentrated by ultrafiltration with a 10 kDa cut-off membrane and purified with DEAE-Sepharose™ FF ion-exchange chromatography and phenyl Seflnose™ 6 FF hydrophobic interaction chromatography. The purified lipase activity reached 5509 U/mg. AOL showed high activity toward short-chain triacylglyceride (C₄), and the optimum temperature and pH were 40 °C and 8.0, respectively. The purified enzyme activity was inhibited by Zn²⁺ and Cu²⁺. Moreover, the K_m and V_max values were 1 mM and 32.89 mmol/min, respectively.

Efficient Heterologous Production of Rhizopus oryzae Lipase via Optimization of Multiple Expression-Related Helper Proteins

This study is dedicated to efficiently produce Rhizopus oryzae lipase (ROL) by optimizing the expression of multiple expression-related helper proteins in Pichia pastoris. A series of engineered strains harboring different copy numbers of the ROL gene and different copies of the chaperone Pdi gene were first constructed to examine the influence of Pdi gene copy number on ROL production. The results showed that multiple copies of Pdi gene did not significantly improve ROL expression. Then, the effect of the co-overexpression of 10 expression-related helper proteins on ROL secretion was investigated by screening 20 colonies of each transformants. The data from shaking-flask fermentation suggested that Ssa4, Bmh2, Sso2, Pdi, Bip, Hac1, and VHb had positive effects on ROL expression. Subsequently, Ssa4, Bmh2, and Sso2, which all participate in vesicular trafficking and strongly promote ROL expression, were combined to further improve ROL production level. ROL activity of the screened strain GS115/5ROL-Ssa4-Sso2-Bmh2 4# attained 5230 U/mL. Furthermore, when the helper proteins Pdi, Bip, Hac1, and VHb were individually co-expressed with ROL in the strain GS115/5ROL-Ssa4-Sso2-Bmh2 4#, lipase activity increased to 5650 U/mL in the strain GS115/5ROL-Ssa4-Sso2-Bmh2-VHb 9#. Additionally, the maximum ROL activity of 41,700 U/mL was achieved in a 3 L bioreactor for high-density fermentation via a sorbitol–methanol co-feeding strategy, reaching almost twofold the value of the initial strain GS115/pAOα-5ROL 11#. Thus, the strategies in this study significantly increased ROL expression level, which is of great potential for the large-scale production of ROL in P. pastoris.

Molecular mechanism of activation of the immunoregulatory amidase NAAA

Palmitoylethanolamide is a bioactive lipid that strongly alleviates pain and inflammation in animal models and in humans. Its signaling activity is terminated through degradation by N-acylethanolamine acid amidase (NAAA), a cysteine hydrolase expressed at high levels in immune cells. Pharmacological inhibitors of NAAA activity exert profound analgesic and antiinflammatory effects in rodent models, pointing to this protein as a potential target for therapeutic drug discovery. To facilitate these efforts and to better understand the molecular mechanism of action of NAAA, we determined crystal structures of this enzyme in various activation states and in complex with several ligands, including both a covalent and a reversible inhibitor. Self-proteolysis exposes the otherwise buried active site of NAAA to allow catalysis. Formation of a stable substrate- or inhibitor-binding site appears to be conformationally coupled to the interaction of a pair of hydrophobic helices in the enzyme with lipid membranes, resulting in the creation of a linear hydrophobic cavity near the active site that accommodates the ligand's acyl chain.

Novel Sanger's Reagent-like Styrene Polymer for the Immobilization of Burkholderia cepacia Lipase

Sanger's reaction, which was originally developed for amino acid detection, was utilized for enzyme immobilization. The newly synthesized polymer support, which was called polymer NO₂-4-fluorostyrene-divinylbenzene (pNFD), was embedded with a Sanger's reagent-like functional group for immobilizing enzymes covalently under mild reaction conditions. Using Burkholderia cepacia lipase (BCL) as the target enzyme, the immobilization efficiency and activity of pNFD-BCL reached as high as 1.2 mg·g^-1 and 33.21 U·g^-1 (a specific activity of 27 675 U·g^-1), respectively, realizing 90% activity recovery. It also improved the optimal reaction temperature of BCL from 40 to 65 °C, under which its full activity could be retained for 4 h. The new carrier also widened the pH-adaptive range of BCL as 6.5-10.0, allowing the lipase to operate normally in weak acid environment. Reusability of pNFD-BCL was significantly improved as almost no activity and/or enantioselectivity loss was observed in 200 h of triglyceride hydrolysis reaction and 17 batches of ( R, S)-1-phenylethanol resolution reaction.

Understanding domain movements and interactions of Pseudomonas aeruginosa lipase with lipid molecule tristearoyl glycerol: A molecular dynamics approach

Lipases are biocatalysts which exhibit optimal activity at the aqueous-lipid interface. Molecular Dynamics (MD) Simulation studies on lipases have revealed the structural changes occurring in the enzyme, at the loop-helix-loop, often designated as the "lid", which is responsible for its interfacial activation. In recent years, MD simulation of lipases at molecular level have been studied in detail, whereas very few studies are carried over on its interaction with lipid molecules. Hence, in the current study we have investigated molecular interaction of bacterial lipase (Pseudomonas aeruginosa lipase, PAL) with a lipid molecule (tristearoyl glycerol, TGL). This provides an insight into the interfacial activation of the enzyme. The lipid molecule was placed near the lids of the enzyme and MD simulations were performed for 100 ns to understand the nature and site of the interaction. The results clearly indicate that, the presence of a lipid molecule near the lids affects the motion of the enzyme through changes in conformation. Lipid molecule near the lids reduces the movements of both lids, and the TGL molecule was observed moving towards the active site. The movement of the lids, surface accessibility and the domain movements of PAL are discussed and the results provide valuable insight in to the role played by the two lids in the interfacial activation of PAL with TGL.

Impacts of Lipase Enzyme on the Surface Properties of Marine Aerosols

Triacylglycerol lipases have recently been shown to be transferred from the ocean to the atmosphere in atmospheric sea spray aerosol (SSA). Lipases have the potential to alter the composition of SSA; however, the structure and properties of enzymes in the high salt, high ionic strength, and low pH conditions found in SSA have never been explored. Here, we study the dynamics of Burkholderia cepacia triacylglycerol lipase (BCL) at SSA model surfaces comprised of palmitic acid and dipalmitoylphosphatidic acid (DPPA), two commonly found lipids at SSA surfaces. Surface adsorption Langmuir isotherm experiments and all-atom explicit solvent molecular dynamics simulations together illuminate how and why BCL expands the ordering of lipids at palmitic acid surfaces the most at pH < 4 and the least in DPPA surfaces at pH 6. Taken together, these results represent a first glimpse into the complex interplay between lipid surface structure and protein dynamics within enzyme-containing aerosols.

Conversion and recovery of saponifiable lipids from microalgae using a nonpolar solvent via lipase-assisted extraction

A single-step method for transesterifying and recovering lipids in concentrated slurries (ca 20% w/w solids) of ruptured microalgae is presented. A soluble Rhizomucor miehei lipase (RML) was used to directly transesterify the lipids in the marine microalgae Nannochloropsis salina. This allowed both triglycerides (TAG) and polar saponifiable lipids to be recovered as fatty acid methyl esters (FAME) using a nonpolar solvent (hexane). Up to 90 wt% of the total saponifiable lipids (SL) were converted to FAME within 24 h, approximately 75% of which was recovered in the hexane by centrifugation. Two pathways for the conversion and recovery of polar lipids were identified. The water in the slurry buffered against potential lipase inhibition by methanol, but necessitated a high methanol dose for maximal FAME conversion. Nonetheless the method enables the recovery of polar lipids as FAME while avoiding the need for both drying of the biomass and a downstream transesterification step.

Spatially confined lignin nanospheres for biocatalytic ester synthesis in aqueous media

Dehydration reactions proceed readily in water-filled biological cells. Development of biocatalysts that mimic such compartmentalized reactions has been cumbersome due to the lack of low-cost nanomaterials and associated technologies. Here we show that cationic lignin nanospheres function as activating anchors for hydrolases, and enable aqueous ester synthesis by forming spatially confined biocatalysts upon self-assembly and drying-driven aggregation in calcium alginate hydrogel. Spatially confined microbial cutinase and lipase retain 97% and 70% of their respective synthetic activities when the volume ratio of water to hexane increases from 1:1 to 9:1 in the reaction medium. The activity retention of industrially most frequently used acrylic resin-immobilized Candida antarctica lipase B is only 51% under similar test conditions. Overall, our findings enable fabrication of robust renewable biocatalysts for aqueous ester synthesis, and provide insight into the compartmentalization of diverse heterogeneous catalysts.

Development of biocatalysts that mimic compartmentalized reactions in cells has been cumbersome due to the lack of low-cost materials and associated technologies. Here the authors show that cationic lignin nanospheres function as activating anchors for hydrolases, and enable aqueous ester synthesis by forming spatially confined biocatalysts.

Spatially confined lignin nanospheres for biocatalytic ester synthesis in aqueous media

Dehydration reactions proceed readily in water-filled biological cells. Development of biocatalysts that mimic such compartmentalized reactions has been cumbersome due to the lack of low-cost nanomaterials and associated technologies. Here we show that cationic lignin nanospheres function as activating anchors for hydrolases, and enable aqueous ester synthesis by forming spatially confined biocatalysts upon self-assembly and drying-driven aggregation in calcium alginate hydrogel. Spatially confined microbial cutinase and lipase retain 97% and 70% of their respective synthetic activities when the volume ratio of water to hexane increases from 1:1 to 9:1 in the reaction medium. The activity retention of industrially most frequently used acrylic resin-immobilized Candida antarctica lipase B is only 51% under similar test conditions. Overall, our findings enable fabrication of robust renewable biocatalysts for aqueous ester synthesis, and provide insight into the compartmentalization of diverse heterogeneous catalysts.

Novel amphiphilic polyvinylpyrrolidone functionalized silicone particles as carrier for low-cost lipase immobilization

The high catalytic activity, specificity and stability of immobilized lipase have been attracting great interest. How to reduce the cost of support materials has always been a hot topic in this field. Herein, for the development of low-cost immobilized lipase, we demonstrate an amphiphilic polyvinylpyrrolidone (PVP) grafted on silicone particle (SP) surface materials (SP-PVP) with a rational design based on interfacial activation and solution polymerization. Meanwhile, hydrophilic pristine SP and hydrophobic polystyrene-corded silicone particles (SP-Pst) were also prepared for lipase immobilization. SP-PVP was characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and thermogravimetry. Our results indicated that the lipase loading amount on the SP-PVP composites was about 215 mg of protein per gram. In the activity assay, the immobilized lipase SP-PVP@CRL exhibited higher catalysis activity and better thermostability and reusability than SP@CRL and SP-Pst@CRL. The immobilized lipase retained more than 54% of its initial activity after 10 times of re-use and approximately trended to a steady rate in the following cycles. By introducing the interesting amphiphilic polymer to this cheap and easily obtained SP surface, the relative performance of the immobilized lipase can be significantly improved, facilitating interactions between the low-cost support materials and lipase.

pH-Induced Rotation of Lidless Lipase LipA from Bacillus subtilis at Lipase-Detergent Interface

Lipases exhibit a unique process during the catalysis of the hydrolysis of triglyceride substrates called interfacial activation. Surfactants are used as cosolvents with water not only to offer a less polar environment to the lipases needed for their interfacial activation but also to solvate the substrate which are poorly soluble in water. However, the presence of detergent in the medium can affect both the lipase and the substrate, making the construction of a microkinetic model for lipase activity in the presence of the detergent difficult. Herein, we study the interfacial activation of a lidless lipase LipA from Bacillus subtilis using extensive atomistic molecular dynamics simulations at different concentrations of the surfactant, Thesit (C12E8), at two pH values. Residues which bind to the monomeric detergent are found to be the same as the ones which have been reported earlier to bind to the substrate. Very importantly, a pH-induced rotation of the enzyme with respect to surfactant aggregate has been observed which not only explains the experimentally observed pH-dependent enzymatic activity of this lidless lipase, but also suggests its reorientation at an aqueous-lipodophilic interface.

Performance of Different Immobilized Lipases in the Syntheses of Short- and Long-Chain Carboxylic Acid Esters by Esterification Reactions in Organic Media

Short-chain alkyl esters and sugar esters are widely used in the food, pharmaceutical and cosmetic industries due to their flavor and emulsifying characteristics, respectively. Both compounds can be synthesized via biocatalysis using lipases. This work aims to compare the performance of commercial lipases covalently attached to dry acrylic beads functionalized with oxirane groups (lipases from Candida antarctica type B-IMMCALB-T2-350, Pseudomonas fluorescens-IMMAPF-T2-150, and Thermomyces lanuginosus-IMMTLL-T2-150) and a home-made biocatalyst (lipase from Pseudomonas fluorescens adsorbed onto silica coated with octyl groups, named PFL-octyl-silica) in the syntheses of short- and long-chain carboxylic acid esters. Esters with flavor properties were synthetized by esterification of acetic and butyl acids with several alcohols (e.g., ethanol, 1-butanol, 1-hexanol, and isoamyl alcohol), and sugar esters were synthetized by esterification of oleic and lauric acids with fructose and lactose. All biocatalysts showed similar performance in the syntheses of short-chain alkyl esters, with conversions ranging from 88.9 to 98.4%. However, in the syntheses of sugar esters the performance of PFL-octyl-silica was almost always lower than the commercial IMMCALB-T2-350, whose conversion was up to 96% in the synthesis of fructose oleate. Both biocatalysts showed high operational stability in organic media, thus having great potential for biotransformations.

Many Ways to Derivatize Macromolecules and Their Crystals for Phasing

Due to the availability of many macromolecular models in the Protein Data Bank, the majority of crystal structures are currently solved by molecular replacement. However, truly novel structures can only be solved by one of the versions of the special-atom method. The special atoms such as sulfur, phosphorus or metals could be naturally present in the macromolecules, or could be intentionally introduced in a derivatization process. The isomorphous and/or anomalous scattering of X-rays by these special atoms is then utilized for phasing. There are many ways to obtain potentially useful derivatives, ranging from the introduction of special atoms to proteins or nucleic acids by genetic engineering or by chemical synthesis, to soaking native crystals in solutions of appropriate compounds with heavy and/or anomalously scattering atoms. No approach guarantees the ultimate success and derivatization remains largely a trial-and-error process. In practice, however, there is a very good chance that one of a wide variety of the available procedures will lead to successful structure solution.

Synergistic effect of mutagenesis and truncation to improve a polyesterase from Clostridium botulinum for polyester hydrolysis

The activity of the esterase (Cbotu_EstA) from Clostridium botulinum on the polyester poly(ethylene terephthalate) (PET) was improved by concomitant engineering of two different domains. On the one hand, the zinc-binding domain present in Cbotu_EstA was subjected to site-directed mutagenesis. On the other hand, a specific domain consisting of 71 amino acids at the N-terminus of the enzyme was deleted. Interestingly, a combination of substitution of residues present in the zinc-binding domain (e.g. S199A) synergistically increased the activity of the enzyme on PET seven fold when combined to the truncation of 71 amino acids at the N-terminus of the enzyme only. Overall, when compared to the native enzyme, the combination of truncation and substitutions in the zinc-binding domain lead to a 50-fold activity improvement. Moreover, analysis of the kinetic parameters of the Cbotu_EstA variants indicated a clear shift of activity from water soluble (i.e. para-nitrophenyl butyrate) to insoluble polymeric substrates. These results evidently show that the interaction with non-natural polymeric substrates provides targets for enzyme engineering.

Engineering aspects of immobilized lipases on esterification: A special emphasis of crowding, confinement and diffusion effects

Cross-linked enzyme crystal (CLEC) and sol-gel entrapped pseudomonas sp. lipase were investigated for the esterification of lauric acid with ethanol by considering the effects of reaction conditions on reaction rate. The activation energy for the reaction was estimated to be 1097.58 J/mol and 181.75 J/mol for sol-gel and CLEC entrapped lipase respectively. CLEC lipase exhibited a marginal internal diffusion effect on reaction rate over sol-gel lipases and found to be interesting. The overall reaction mechanism was found to conform to the Ping Pong Bi Bi mechanism. The higher efficiency of sol-gel lipases over CLEC lipases in esterification reaction is mainly due to the combined effects of crowding, confinement and diffusional limitations.

High-level extracellular production of Rhizopus oryzae lipase in Pichia pastoris via a strategy combining optimization of gene-copy number with co-expression of ERAD-related proteins

Rhizopus oryzae lipase (ROL) is an important industrial enzyme limited in application due to its low production in native strains. Here, we used a new combined strategy to overexpress ROL in Pichia pastoris. An efficient method based on bio-brick was developed to construct a series of vectors harboring different copy numbers of ROL gene cassettes, which were then transformed into P. pastoris GS115 to generate a strain with specific copy numbers of ROL. An optimized gene-dosage recombinant strain of GS115/pAOα-5ROL 11# harboring five copies of ROL was screened, revealing production of the highest activity (2700 U/mL), which was 8-fold higher than that of the strain harboring one copy. The activity of GS115/pAOα-5ROL 11# was then enhanced to 3080 U/mL in a shaking flask under optimized culture conditions. Subsequently, the endoplasmic reticulum-associated protein-degradation-related genes Ubc1 or/and Hrd1 were co-expressed with ROL to further increase ROL expression. The activities of the recombinant strains, GS115/5ROL-Ubc1 22#, -Hrd1 15#, and -Hrd1-Ubc1 1#, were 4000 U/mL, 4200 U/mL, and 4750 U/mL, which was 29.9%, 36.4%, and 54.2% higher, respectively, than that observed in GS115/pAOα-5ROL 11#. Using the combined strategy, ROL expression was improved 15.8-fold, with maximum GS115/5ROL-Hrd1-Ubc1 1# activity reaching 33,900 U/mL via a sorbitol/methanol co-feeding strategy in a 3-L fermenter and resulting in a 1.65-, 1.26-, and 1.14-fold enhancement relative to the activities observed in strains GS115/pAOα-5ROL 11#, GS115/5ROL-Ubc1 22#, and GS115/5ROL-Hrd1 15#, respectively. These results indicated that heterologous overexpression of ROL in P. pastoris using this combined strategy is feasible for large-scale industrialization.