Anatomy of lipase binding sites: the scissile fatty acid binding site

Immobilisation of Candida rugosa lipase on a highly hydrophobic support: A stable immobilised lipase suitable for non-aqueous synthesis

Lipase from Candida rugosa (CrL) was immobilised on highly hydrophobic, octadecyl methacrylate resin (Lifetech™ ECR8806M) via interfacial adsorption. The aim was to produce a stable biocatalyst suitable for use in a range of lipid-modifying reactions. Immobilisation was carried out in 10 mM phosphate buffer (pH 6.0) over 24 h at 21 °C. High protein binding of 58.7 ± 4.9 mg/g dry support accounted for ∼53 % of the applied protein. The activity recovery against tributyrin was 74.0 ± 1.1 %. The specific activity of immobilised CrL against tributyrin was considerably higher than that of Novozym® 435, at 1.79 ± 0.05 and 1.08 ± 0.04 U/mg bound protein, respectively. Incubation with high concentrations (10 % w/v) of both Triton X-100 and SDS resulted in only a small reduction in immobilised lipase activity. Solvent-free synthesis of glycerides by the FFA-saturated immobilised CrL was successful over 6 reaction cycles, with no apparent loss of activity.

Enzymatically-synthesized xylo-oligosaccharides laurate esters as surfactants of interest

Lipase-catalyzed synthesis of xylo-oligosaccharides esters from pure xylobiose, xylotriose and xylotetraose in the presence of vinyl laurate was investigated. The influence of different experimental parameters such as the loading of lipase, the reaction duration or the use of a co-solvent was studied and the reaction conditions were optimized with xylobiose. Under the best conditions, a regioselective esterification occurred to yield a monoester with the acyl chain at the OH-4 of the xylose unit at the non-reducing end. Surface-active properties of these pure xylo-oligosaccharides fatty esters have been evaluated. They display interesting surfactant activities that differ according to the degree of polymerization (DP) of the glycone moiety.

Main Structural Targets for Engineering Lipase Substrate Specificity

Microbial lipases represent one of the most important groups of biotechnological biocatalysts. However, the high-level production of lipases requires an understanding of the molecular mechanisms of gene expression, folding, and secretion processes. Stable, selective, and productive lipase is essential for modern chemical industries, as most lipases cannot work in different process conditions. However, the screening and isolation of a new lipase with desired and specific properties would be time consuming, and costly, so researchers typically modify an available lipase with a certain potential for minimizing cost. Improving enzyme properties is associated with altering the enzymatic structure by changing one or several amino acids in the protein sequence. This review detailed the main sources, classification, structural properties, and mutagenic approaches, such as rational design (site direct mutagenesis, iterative saturation mutagenesis) and direct evolution (error prone PCR, DNA shuffling), for achieving modification goals. Here, both techniques were reviewed, with different results for lipase engineering, with a particular focus on improving or changing lipase specificity. Changing the amino acid sequences of the binding pocket or lid region of the lipase led to remarkable enzyme substrate specificity and enantioselectivity improvement. Site-directed mutagenesis is one of the appropriate methods to alter the enzyme sequence, as compared to random mutagenesis, such as error-prone PCR. This contribution has summarized and evaluated several experimental studies on modifying the substrate specificity of lipases.

Label-Free Fluorescence Quantification of Hydrolytic Enzyme Activity on Native Substrates Reveals How Lipase Function Depends on Membrane Curvature

Lipases are important hydrolytic enzymes used in a spectrum of technological applications, such as the pharmaceutical and detergent industries. Because of their versatile nature and ability to accept a broad range of substrates, they have been extensively used for biotechnological and industrial applications. Current assays to measure lipase activity primarily rely on low-sensitivity measurements of pH variations or visible changes of material properties, like hydration, and often require high amounts of proteins. Fluorescent readouts, on the other hand, offer high contrast and even single-molecule sensitivity, albeit they are reliant on fluorogenic substrates that structurally resemble the native ones. Here we present a method that combines the highly sensitive readout of fluorescent techniques while reporting enzymatic lipase function on native substrates. The method relies on embedding the environmentally sensitive fluorescent dye pHrodo and native substrates into the bilayer of liposomes. The charged products of the enzymatic hydrolysis alter the local membrane environment and thus the fluorescence intensity of pHrodo. The fluorescence can be accurately quantified and directly assigned to product formation and thus enzymatic activity. We illustrated the capacity of the assay to report the function of diverse lipases and phospholipases both in a microplate setup and at the single-particle level on individual nanoscale liposomes using total internal reflection fluorescence (TIRF). The parallelized sensitive readout of microscopy combined with the inherent polydispersity in sizes of liposomes allowed us to screen the effect of membrane curvature on lipase function and identify how mutations in the lid region control the membrane curvature-dependent activity. We anticipate this methodology to be applicable for sensitive activity readouts for a spectrum of enzymes where the product of the enzymatic reaction is charged.

The Effectively Simultaneous Production of Cello-oligosaccharide and Glucose Mono-decanoate from Lignocellulose by Enzymatic Esterification

Cello-oligosaccharide has drawn an increasing attention as the nutritional ingredients of dietary supplements, whose quality is affected by the concentration of monosaccharide. In the present study, an effective process was developed for the simultaneous production of cello-oligosaccharide and glucose mono-decanoate from lignocellulose by enzymatic esterification. During the process, the excessive glucose in cello-oligosaccharide was converted into glucose mono-decanoate, which is a well-known biodegradable nonionic surfactant. The filter paper was initially used as the model to investigate the feasibility of the process, in which the purity of resultant cello-oligosaccharide was increased from 33.3% to 74.3%, simultaneously producing glucose mono-decanoate with a purity of 92.3%. Further verification of 3 kinds of lignocelluloses (switchgrass, cornstalk, and reed) also indicated a good performance of the process. The present process provided an effective strategy to increase the purity of resultant cello-oligosaccharide with the simultaneous production of high value-added products of sugar monoester. Graphical Abstract Simultaneous production of cello-oligosaccharide and glucose mono-decanoate from lignocellulose.

Exploring the Enzymatic and Antibacterial Activities of Novel Mycobacteriophage Lysin B Enzymes

Mycobacteriophages possess different sets of lytic enzymes for disruption of the complex cell envelope of the mycobacteria host cells and release of the viral progeny. Lysin B (LysB) enzymes are mycolylarabinogalactan esterases that cleave the ester bond between the arabinogalactan and mycolic acids in the mycolylarabinogalactan-peptidoglycan (mAGP) complex in the cell envelope of mycobacteria. In the present study, four LysB enzymes were produced recombinantly and characterized with respect to their enzymatic and antibacterial activities. Examination of the kinetic parameters for the hydrolysis of para-nitrophenyl ester substrates, shows LysB-His₆ enzymes to be active against a range of substrates (C4–C16), with a catalytic preference towards p-nitrophenyl laurate (C12). With p-nitrophenyl butyrate as substrate, LysB-His₆ enzymes showed highest activity at 37 °C. LysB-His₆ enzymes also hydrolyzed different Tween substrates with highest activity against Tween 20 and 80. Metal ions like Ca²⁺ and Mn²⁺ enhanced the enzymatic activity of LysB-His₆ enzymes, while transition metal ions like Zn²⁺ and Cu²⁺ inhibited the enzymatic activity. The mycolylarabinogalactan esterase activity of LysB-His₆ enzymes against mAGP complex was confirmed by LC-MS. LysB-His₆ enzymes showed marginal antibacterial activity when tested alone against Mycobacterium smegmatis, however a synergetic activity was noticed when combined with outer membrane permealizers. These results confirm that LysB enzymes are lipolytic enzymes with potential application as antimycobacterials.

Substrate structure and computation guided engineering of a lipase for omega-3 fatty acid selectivity

Enrichment of omega-3 fatty acids (ɷ-3 FAs) in natural oils is important to realize their health benefits. Lipases are promising catalysts to perform this enrichment, however, fatty acid specificity of lipases is poor. We attempted to improve the fatty acid selectivity of a lipase from Geobacillus thermoleovorans (GTL) by two approaches. In a semi-rational approach, amino acid positions critical for binding were identified by docking the substrate to the GTL and best substitutes at these positions were identified by site saturation mutagenesis followed by screening to obtain a variant of GTL (CM-GTL). In the second approach based on rational design, a variant of GTL was designed (DM-GTL) wherein the active site was narrowed by incorporating two heavier amino acids in the lining of acyl-binding pocket to hinder access to bulky ɷ-3 FAs. The affinities DM-GTL with designed substrates were evaluated in silico. Both, CM-GTL and DM-GTL have shown excellent ability to discriminate against the ɷ-3 FAs during hydrolysis of oils. Engineering the binding pocket of an enzyme of a complex substrate, such as a triglyceride, by incorporating the information on substrate structure and computationally derived binding modes, has resulted in designing two efficient lipase variants with improved substrate selectivity.

Cutinases as stereoselective catalysts: Specific activity and enantioselectivity of cutinases and lipases for menthol and its analogs

The specific activity and enantioselectivity of immobilized cutinases from Aspergillus oryzae (AoC) and Humicola insolens (HiC) were compared with those of lipases from Thermomyces lanuginosus (TLL), Rhizomucor miehei (RML) and Lipase B from Candida antarctica (CALB) for menthol and its analogs that include isopulegol, trans-2-tert-butylcyclohexanol (2TBC), and dihydrocarveol (DHC). Common features of these alcohols are two bulky substituents: a cyclohexyl ring and an alkyl substituent. Dissimilarities are that the alkyl group reside at different positions or have dissimilar structures. The aim was to develop an understanding at a molecular level of similarities and differences in the catalytic behavior of the selected cutinases and lipases as a function of substrate structural elements. The experimental results reflect the (-)-enantioselectivity for AoC, HiC, TLL, and RML, while CALB is only active on DHC with (+)-enantioselectivity. In most cases, AoC has the highest activity while HiC is significantly more active than other enzymes on 2TBC. The E values of AoC, HiC, TLL, and RML for menthol are 27.8, 16.5, 155, and 125, respectively. HiC has a higher activity (>10-fold) on (-)-2TBC than AoC while they exhibit similar activities on menthol. Docking results reveal that the bulky group adjacent to the hydroxyl group determines the enantioselectivity of AoC, HiC, TLL, and RML. Amino acid residues that dominate the enantioselectivity of these enzymes are AoC's Phe195 aromatic ring; HiC's hydrophobic Leu 174 and Ile 169 groups; TLL's ring structures of Trp89, His258 and Tyr21; and Trp88 for RML. Results of this study highlight that cutinases can provide important advantages relative to lipases for enantioselective transformation, most notably with bulky and sterically hindered substrates.

Comparative Structural Analysis of Different Mycobacteriophage-Derived Mycolylarabinogalactan Esterases (Lysin B)

Mycobacteriophage endolysins have emerged as a potential alternative to the current antimycobacterial agents. This study focuses on mycolylarabinogalactan hydrolase (LysB) enzymes of the α/β-hydrolase family, which disrupt the unique mycolic acid layer of mycobacterium cell wall. Multiple sequence alignment and structural analysis studies showed LysB-D29, the only enzyme with a solved three-dimensional structure, to share several common features with esterases (lacking lid domain) and lipases (acting on long chain lipids). Sequence and structural comparisons of 30 LysB homology models showed great variation in domain organizations and total protein length with major differences in the loop-5 motif harboring the catalytic histidine residue. Docking of different p-nitrophenyl ligands (C4-C18) to LysB-3D models revealed that the differences in length and residues of loop-5 contributed towards wide diversity of active site conformations (long tunnels, deep and superficial funnels, shallow bowls, and a narrow buried cave) resembling that of lipases, cutinases, and esterases. A set of seven LysB enzymes were recombinantly produced; their activity against p-nitrophenyl esters could be related to their active site conformation and acyl binding site. LysB-D29 (long tunnel) showed the highest activity with long chain p-nitrophenyl palmitate followed by LysB-Omega (shallow bowl) and LysB-Saal (deep funnel).

Integrated Production of Biodiesel and Concentration of Polyunsaturated Fatty Acid in Glycerides Through Effective Enzymatic Catalysis

DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid) contained in glycerides have been reported to be more advantageous for their intake than their counterpart in the form of free fatty acid or fatty acid esters. This work attempts to achieve the flexible concentration of DHA and EPA in glycerides as well as biodiesel production via a two-step process catalyzed by lipases. In the first step, several commercial lipases were investigated and Novozym ET2.0 demonstrated the highest potential in selective concentration of DHA and EPA. Over 85% of EPA and other fatty acids were converted to its corresponding FAEEs (fatty acid ethyl esters), while over 80% of DHA remained in glycerides under the optimized conditions. After the first step ethanolysis, the oil phase was subject to molecular distillation and a 97.5% biodiesel (FAEE) content could be obtained. Further flexible enrichment of DHA and EPA in glycerides was realized by immobilized lipase Novozym 435-mediated transesterification of glycerides (remaining in the heavy phase after molecular distillation) with DHA- or EPA-rich EE, and glycerides with 67.1% DHA and 13.1% EPA, or glycerides with 41.1% EPA and 38.0% DHA could be obtained flexibly. This work demonstrated an effective approach for DHA and EPA enrichment combined with biodiesel production through enzymatic catalysis.

Screening of solvents for favoring hydrolytic activity of Candida antarctica Lipase B

Lipases are a group of enzymes of considerable significance in organic synthesis, among which Candida antarctica lipase B (CALB) is one of the most widely studied enzymes. The activity of the biocatalyst has been intensively characterized in many organic media, but this paper aimed to compare the effect of 20 different solvents on the activity of CALB in the hydrolysis of p-nitrophenyl laurate. Nonpolar, polar aprotic, and polar protic solvents were used for enzyme pretreatment and then entered the composition of mixed solvents reaction medium. An impact of solvents on solvation processes affecting the catalysis steps, protein denaturation, and changes of its conformation was discussed. Moreover the hydrolytic activity of CALB with partition coefficient (logP) of the solvent used was correlated. It was emphasized that the substrate solubility plays an important role in solvent selection. In the presence of hydrophobic solvents, hydration layer becomes more hydrophobic facilitating the substrate access to the enzyme surface. In turn, polar compounds are good solvents for organic substrates facilitating the penetration of the aqueous layer that surrounds the surface of the enzyme. Two variants proved to be favorable for ester hydrolysis reaction: isooctane or polar solvent such as acetone, tert -butyl methyl ether, tert-butanol or acetonitrile.

Production of biodiesel by enzymatic transesterification of non-edible Salvadora persica (Pilu) oil and crude coconut oil in a solvent-free system

Background

It is becoming imperative to develop renewable fuels such as biodiesel which are sustainable and environmentally friendly. Exploiting non-edible oils is more necessary to reduce dependency of edible oils for biodiesel production. The current study investigated biodiesel production from non-edible Salvadora persica seed oil (SPSO) and crude coconut oil (CCO) by Burkholderia cepacia lipase acting as a biocatalyst in a solvent-free system. The biodiesel yield produced from these feedstocks was compared and the effect of ethanol (acyl acceptor) vs. SPSO and CCO in various ratios on biodiesel production was determined.

Results

The presence of medium-chain fatty acids in majority was confirmed for SPSO and CCO while the average molecular weight was calculated as 749.53 g/mol and 664.57 g/mol, respectively. Thin Layer Chromatography indicated ethyl esters in the produced Salvadora and coconut biodiesel samples. Maximum biodiesel yield (around 70%) was obtained at 1:4 oil-to-ethanol molar ratio from both oils followed by a decline at higher ratios. The gas chromatographic analysis of Salvadora biodiesel at 1:4 molar ratio showed that the yield of individual esters was mostly of medium- and long-chain fatty acids. The analysis of coconut biodiesel at 1:4 molar ratio revealed that it consists mainly of the esters of medium-chain fatty acids. A comparison of estimated properties of biodiesel from both the parent oils with the international standard showed that it meets most of the requirements.

Conclusion

The study paves the way for a green route for biodiesel production and would promote the use of non-edible vegetable oils over edible ones to produce biodiesel. Further, it is a right step to use lipases in biodiesel production as compared to chemical catalysts. Ethanol, which can also be produced from biomass fermentation, can be used as acyl acceptor to produce biodiesel and this makes the process eco-friendly. Moreover, Burkholderia cepacia lipase is a good choice among lipases to get high biodiesel yields successfully from SPSO and CCO at low oil-to-ethanol molar ratios.

Biocatalytic Synthesis of Lipophilic Baicalin Derivatives as Antimicrobial Agents

Enzymatic acylation is commonly used to increase the lipophilicity of flavonoids. However, the absence of primary hydroxyl groups makes it challenging to acylate baicalin using traditional acylation methods. In this study, an enzymatic esterification strategy was developed to introduce fatty-acid chains into baicalin at its carboxyl group, hence successfully synthesizing a new series of baicalin ester derivatives in nonaqueous media. Under the optimal reaction conditions, up to 95% conversion of baicalin was achieved. Antimicrobial evaluation of the baicalin ester derivatives indicated a corresponding increase to that of C log P values, with a cutoff effect at C log P = 5.2. Baicalin ester derivatives with C log P values of 4.9-5.2 exhibited the most potent antimicrobial activity. Interestingly, the introduction of medium-length fatty alcohol chains not only increased lipophilicity but also endowed them with membrane-disrupting properties. This study, therefore, provides an understanding of the esterification of flavonoid glycosides and a prospective application of the ester derivatives.

Engineering enzyme access tunnels

Enzymes are efficient and specific catalysts for many essential reactions in biotechnological and pharmaceutical industries. Many times, the natural enzymes do not display the catalytic efficiency, stability or specificity required for these industrial processes. The current enzyme engineering methods offer solutions to this problem, but they mainly target the buried active site where the chemical reaction takes place. Despite being many times ignored, the tunnels and channels connecting the environment with the active site are equally important for the catalytic properties of enzymes. Changes in the enzymatic tunnels and channels affect enzyme activity, specificity, promiscuity, enantioselectivity and stability. This review provides an overview of the emerging field of enzyme access tunnel engineering with case studies describing design of all the aforementioned properties. The software tools for the analysis of geometry and function of the enzymatic tunnels and channels and for the rational design of tunnel modifications will also be discussed. The combination of new software tools and enzyme engineering strategies will provide enzymes with access tunnels and channels specifically tailored for individual industrial processes.

Lepidine B & E as New Target Inhibitors from Lepidium Sativum Seeds Against Four Enzymes of the Pathogen Candida albicans: In Vitro and In Silico Studies

BACKGROUND AND OBJECTIVE

The present paper aims to study the inhibition of Candida albicans growth as candidiasis treatment, using seeds of Lepidium sativum as source.

METHODS

In vitro assays were carried out on the antifungal activity of three kinds of extracts from L. sativum seeds against four strains of C. albicans, then testing the same phytochemicals on the inhibition of Lipase (LCR). A new in silico study was achieved using molecular docking, with Autodock vina program, to find binding affinity of two important and major lepidine alkaloids (lepidine E and B) towards the four enzymes secreted by C. albicans as target drugs, responsible of vitality and virulence of this yeast cells: Lipase, Serine/threonine phosphatase, Phosphomannose isomerase and Sterol 14-alpha demethylase (CYP51).

RESULTS

The results of the microdillution assay show that the hexanic and alkaloidal extracts have an antifungal activity with MICs: 2.25 mg/ml and 4.5mg/ml, respectively. However, Candida rugosa lipase assay gives a remarkable IC50 values for the hexanic extract (1.42± 0.04 mg/ml) followed by 1.7± 0.1 and 2.29 ± 0.09 mg/ml of ethyl acetate and alkaloidal extracts respectively. The molecular docking confirms a significant correlation between C. albicans growth and inhibition of crucial enzymes involved in the invasion mechanism and cellular metabolisms, for the first time there were an interesting and new positive results on binding modes of lepidine E and B on the four studied enzymes.

CONCLUSION

Through this work, we propose Lepidine B & E as potent antifungal drugs.

Biotic and Abiotic Synthesis of Renewable Aliphatic Polyesters from Short Building Blocks Obtained from Biotechnology

Biobased polymers have seen their attractiveness increase in recent decades thanks to the significant development of biorefineries to allow access to a wide variety of biobased building blocks. Polyesters are one of the best examples of the development of biobased polymers because most of them now have their monomers produced from renewable resources and are biodegradable. Currently, these polyesters are mainly produced by using traditional chemical catalysts and harsh conditions, but recently greener pathways with nontoxic enzymes as biocatalysts and mild conditions have shown great potential. Bacterial polyesters, such as poly(hydroxyalkanoate)s (PHA), are the best example of the biotic production of high molar mass polymers. PHAs display a wide variety of macromolecular architectures, which allow a large range of applications. The present contribution aims to provide an overview of recent progress in studies on biobased polyesters, especially those made from short building blocks, synthesized through step-growth polymerization. In addition, some important technical aspects of their syntheses through biotic or abiotic pathways have been detailed.

Alteration of Chain Length Selectivity of Candida antarctica Lipase A by Semi-Rational Design for the Enrichment of Erucic and Gondoic Fatty Acids

Biotechnological strategies using renewable materials as starting substrates are a promising alternative to traditional oleochemical processes for the isolation of different fatty acids. Among them, long chain mono-unsaturated fatty acids are especially interesting in industrial lipid modification, since they are precursors of several economically relevant products, including detergents, plastics and lubricants. Therefore, the aim of this study was to develop an enzymatic method in order to increase the percentage of long chain mono-unsaturated fatty acids from Camelina and Crambe oil ethyl ester derivatives, by using selective lipases. Specifically, the focus was on the enrichment of gondoic (C20:1 cisΔ11) and erucic acid (C22:1 cisΔ13) from Camelina and Crambe oil derivatives, respectively. The pursuit of this goal entailed several steps, including: (i) the choice of a suitable lipase scaffold to serve as a protein engineering template (Candida antarctica lipase A); (ii) the identification of potential amino acid targets to disrupt the binding tunnel at the adequate location; (iii) the design, creation and high-throughput screening of lipase mutant libraries; (iv) the study of the selectivity towards different chain length p-nitrophenyl fatty acid esters of the best hits found, as well as the analysis of the contribution of each amino acid change and the outcome of combining several of the aforementioned residue alterations and, finally, (v) the selection and application of the most promising candidates for the fatty acid enrichment biocatalysis. As a result, enrichment of C22:1 from Crambe ethyl esters was achieved either, in the free fatty acid fraction (wt, 78%) or in the esterified fraction (variants V1, 77%; V9, 78% and V19, 74%). Concerning the enrichment of C20:1 when Camelina oil ethyl esters were used as substrate, the best variant was the single mutant V290W, which doubled its content in the esterified fraction from approximately 15% to 34%. A moderately lower increase was achieved by V9 and its two derived triple mutant variants V19 and V20 (27%).

Screening, purification and characterization of lipase from Burkholderia pyrrocinia B1213

A lipase producing strain B1213 isolated from soil was identified as Burkholderia pyrrocinia based on 16S rRNA gene and recA sequeence analysis, making this the first report on the presence of a lipase from B. pyrrocinia. Under an aqueous two-phase purification strategy, which included (ATPE)-ion-exchange chromatography (IEC)-gel and filtration chromatography (GFC), the specific activity of the 35-kDa lipase was determined to be 875.7 U/mg protein. The optimum pH and temperature of this lipase was pH 8.0 and 50 °C, respectively. The lipase retained > 85% activity in isopropanol and acetone at 30 °C for 10 min but the activity was reduced to 10.6% in n-hexane. Mg²⁺, Al³⁺, Mn²⁺, and Fe³⁺ enhanced lipase activity at both 1 mM and 5 mM concentrations. p-NPP, a long-chain acyl group 4-NP ester, appeared to be a good substrate candidate.

Enzymatic Acylation of Anthocyanins Isolated from Alpine Bearberry ( Arctostaphylos alpina) and Lipophilic Properties, Thermostability, and Antioxidant Capacity of the Derivatives

Cyanidin-3- O-galactoside (cy-gal) isolated from alpine bearberry ( Arctostaphylos alpine L.) was enzymatically acylated with saturated fatty acids of different chain lengths with Candida antarctica lipase immobilized on acrylic resin (Novozyme 435). The acylation reaction was optimized by considering the reaction medium, acyl donor, substrate molar ratio, reaction temperature, and reaction time. The highest conversion yield of 73% was obtained by reacting cy-gal with lauric acid (molar ratio of 1:10) in tert-butanol at 60 °C for 72 h. A novel compound was synthesized, which was identified as cyanidin-3- O-(6″-dodecanoyl)galactoside by mass spectrometry and nuclear magnetic resonance. Introducing lauric acid into cy-gal significantly improved both the lipophilicity and thermostability and substantially preserved the ultraviolet-visible absorbance and antioxidant properties. The research provides important insight in expanding the application of natural anthocyanins in the cosmetic and food industries.

Structural Mechanism for the Temperature-Dependent Activation of the Hyperthermophilic Pf2001 Esterase

Lipases and esterases constitute a group of enzymes that catalyze the hydrolysis or synthesis of ester bonds. A major biotechnological interest corresponds to thermophilic esterases, due to their intrinsic stability at high temperatures. The Pf2001 esterase from Pyrococcus furiosus reaches its optimal activity between 70°C and 80°C. The crystal structure of the Pf2001 esterase shows two different conformations: monomer and dimer. The structures reveal important rearrangements in the "cap" subdomain between monomer and dimer, by the formation of an extensive intertwined helical interface. Moreover, the dimer interface is essential for the formation of the hydrophobic channel for substrate selectivity, as confirmed by mutagenesis and kinetic analysis. We also provide evidence for dimer formation at high temperatures, a process that correlates with its enzymatic activation. Thus, we propose a temperature-dependent activation mechanism of the Pf2001 esterase via dimerization that is necessary for the substrate channel formation in the active-site cleft.

Lipases: An Overview

Lipases are ubiquitous enzymes, widespread in nature. They were first isolated from bacteria in the early nineteenth century, and the associated research continuously increased due to the characteristics of these enzymes. This chapter reviews the main sources, structural properties, and industrial applications of these highly studied enzymes.

Production of wax esters via microbial oil synthesis from food industry waste and by-product streams

The production of wax esters using microbial oils was demonstrated in this study. Microbial oils produced from food waste and by-product streams by three oleaginous yeasts were converted into wax esters via enzymatic catalysis. Palm oil was initially used to evaluate the influence of temperature and enzyme activity on wax ester synthesis catalysed by Novozyme 435 and Lipozyme lipases using cetyl, oleyl and behenyl alcohols. The highest conversion yields (up to 79.6%) were achieved using 4U/g of Novozyme 435 at 70°C. Transesterification of microbial oils to behenyl and cetyl esters was achieved at conversion yields up to 87.3% and 69.1%, respectively. Novozyme 435 was efficiently reused for six and three cycles during palm esters and microbial esters synthesis, respectively. The physicochemical properties of microbial oil derived behenyl esters were comparable to natural waxes. Wax esters from microbial oils have potential applications in cosmetics, chemical and food industries.

Kinetic study on the inhibition of xanthine oxidase by acylated derivatives of flavonoids synthesised enzymatically

Studies have reported that flavonoids inhibit xanthine oxidase (XO) activity; however, poor solubility and stability in lipophilic media limit their bioavailability and applications. This study evaluated the kinetic parameters of XO inhibition and partition coefficients of flavonoid esters biosynthesised from hesperidin, naringin, and rutin via enzymatic acylation with hexanoic, octanoic, decanoic, lauric, and oleic acids catalysed by Candida antarctica lipase B (CALB). Quantitative determination by ultra-high performance liquid chromatography–mass spectrometry (UHPLC–MS) showed higher conversion yields (%) for naringin and rutin esters using acyl donors with 8C and 10C. Rutin decanoate had higher partition coefficients (0.95), and naringin octanoate and naringin decanoate showed greater inhibitory effects on XO (IC₅₀ of 110.35 and 117.51 μM, respectively). Kinetic analysis showed significant differences (p < .05) between the flavonoids before and after acylation regarding K_m values, whereas the values for V_max were the same, implying the competitive nature of XO inhibition.

The Lid Domain in Lipases: Structural and Functional Determinant of Enzymatic Properties

Lipases are important industrial enzymes. Most of the lipases operate at lipid–water interfaces enabled by a mobile lid domain located over the active site. Lid protects the active site and hence responsible for catalytic activity. In pure aqueous media, the lid is predominantly closed, whereas in the presence of a hydrophobic layer, it is partially opened. Hence, the lid controls the enzyme activity. In the present review, we have classified lipases into different groups based on the structure of lid domains. It has been observed that thermostable lipases contain larger lid domains with two or more helices, whereas mesophilic lipases tend to have smaller lids in the form of a loop or a helix. Recent developments in lipase engineering addressing the lid regions are critically reviewed here. After on, the dramatic changes in substrate selectivity, activity, and thermostability have been reported. Furthermore, improved computational models can now rationalize these observations by relating it to the mobility of the lid domain. In this contribution, we summarized and critically evaluated the most recent developments in experimental and computational research on lipase lids.