Catalytic characteristics of a sn-1(3) regioselective lipase from Cordyceps militaris

A total of 39 agricultural products were screened for natural sources of lipases with distinctive positional specificity. Based on this, Cordyceps militaris lipase (CML) was selected and subsequently purified by sequential chromatography involving anion-exchange, hydrophobic-interaction, and gel-permeation columns. As a result of the overall purification procedure, a remarkable increase in the specific activity of the CML (4.733 U/mg protein) was achieved, with a yield of 2.47% (purification fold of 94.54). The purified CML has a monomeric structure with a molecular mass of approximately 62 kDa. It was further identified as a putative extracellular lipase from C. militaris by the partial sequence analysis using ESI-Q-TOF MS. In a kinetic study of the CML-catalyzed hydrolysis, the values of V_max, K_m, and k_cat were determined to be 4.86 μmol·min⁻¹·mg⁻¹, 0.07 mM, and 0.29 min⁻¹, respectively. In particular, the relatively low K_m value indicated that CML has a high affinity for its substrate. With regard to positional specificity, CML selectively cleaved triolein at the sn-1 or 3 positions of glycerol backbone, releasing 1,2(2,3)-diolein as the major products. Therefore, CML can be considered a distinctive biocatalyst with sn-1(3) regioselectivity. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2744, 2019.     

Substrate specificity of Staphylococcus aureus (TEN5) lipases with isomeric oleoyl-sn-glycerol ethers as substrates

For the first time fully protected substrates with only one hydrolyzable ester bond have been used to analyze the substrate specificity of microbial lipases. In these substrates the ester is attached to the glycerol molecule in a precisely defined position. The use of three different substituents generates chirality and thus allows the analysis of positional specificities of individual lipases. Therefore, these new substrates have been used to study the enzymatic activities of two closely related lipases isolated from Staphylococcus aureus (TEN5) designated the 44 and 43 kDa lipase. The lipases, especially the 44 kDa molecule, show a high specificity for the hydrolysis of the ester in the sn-1 position (S-configuration), which is hydrolyzed by a factor of ten faster than that in the sn-3 position. In addition, the study demonstrates for the first time that the rate of hydrolysis of a fatty acid ester attached to the sn-2 position of glycerol by microbial lipases depends on the configuration of the substrate molecule.     

Kinetic resolution of (±)-diethyl- and dibenzyl hydroxy(phenyl)methanephosphonates and their acyl derivatives with lipases

Abstract

A wide variety of commercially available lipases and microbial whole cells were tested for biotransformations of (±)-diethyl and dibenzyl hydroxyl(phenyl)methanephosphonates. Biocatalytic hydrolysis of acylated hydroxyphosphonates by whole cells of Bacillus subtilis gave optically active compounds with 95%ee _S. Enantioselectivities obtained when using commercially available enzymatic preparations were less satisfactory, leading to both compounds with an enantiomeric excess in the range 15 35%. Screening lipases for their ability to acylate these phosphonates or to hydrolyze their acylated derivatives enabled selection of enzymes and organisms suitable for use in both processes.     

Enzymatic transesterification in a solvent-free system: synthesis of sn-2 docosahexaenoyl monoacylglycerol

Abstract

The enzymatic transesterification of docosahexaenoic acid (DHA) ethyl ester with glycerol was carried out by using several immobilized lipases in a solvent-free system. This reaction involves the initial formation of sn-2 docosahexaenyl monoacylglycerol. This DHA derivative is highly relevant for improving the bioavailability of DHA and it has received increasing interest in the field of nutrition. Three commercial lipases, from Rhizomucor miehei (RML), Alcaligenes sp. (AQ) and Candida antarctica-fraction B (CALB) were immobilized by interfacial adsorption on a commercial hydrophobic support (a methacrylate resin containing octadecyl groups, Sepabeads C-18) and tested for glycerolysis of DHA ethyl ester. In certain cases (e.g. immobilized CALB), the transesterification reaction continues to the formation of triacylglycerol (80%) by using a very high excess of DHA ethyl ester ((115 mmols versus 1.24 mmols of glycerol and high temperatures (50?°C). However, the same biocatalyst working at lower temperatures, 37?°C, synthetizes a 90% of sn-2 monoacylglycerol even in the presence of that a high excess of DHA ethyl ester. Interestingly, immobilized RML derivative synthesizes a 98% of sn-2 monoacylglyceride (2-MG) in 15?min at 37?°C with a 4% of immobilized biocatalyst. These high activity and regioselectivity under very mild reaction conditions are very interesting for the thermal oxidative stability of the omega-3 fatty acid as well as for the thermal stability of the biocatalyst. Using Normal Phase HPLC-ELSD and accurate commercial markers, the formation of the 2-MG was confirmed.     

Action of leptospiral lipases on purified serum lipoproteins

Partially purified exocellular lipases produced by a pathogenic (Leptospira copenhageni (PB-3) and a saprophytic strain ofLeptospirae (Leptospira Patoc I) hydrolyzed very low density, and to a lesser extent low density hog serum lipoproteins. No high density lipoprotein hydrolysis was found. Optimal conditions for the action of both lipases on very low density serum lipoproteins were determined: pH 8.5; NaCl 0.4m; CaCl₂ 1.0mm; sodium desoxycholate 10.60mm. The maximal velocities of very low density lipoprotein hydrolysis were compared with the maximal velocities of triglyceride emulsion hydrolysis by both lipases.     

Novel chromatographic resolution of chiral diacylglycerols and analysis of the stereoselective hydrolysis of triacylglycerols by lipases

In the present study, we propose a general and accessible method for the resolution of enantiomeric 1,2-sn- and 2,3-sn-diacylglycerols based on derivatization by isocyanates, which can be easily used routinely by biochemists to evaluate the stereopreferences of lipases in a time course of triacylglycerol (TAG) hydrolysis. Diacylglycerol (DAG) enantiomers were transformed into carbamates using achiral and commercially available reagents. Excellent separation and resolution factors were obtained for diacylglycerols present in lipolysis reaction mixtures. This analytical method was then applied to investigate the stereoselectivity of three model lipases (porcine pancreatic lipase, PPL; lipase from Rhizomucor miehei, MML; and recombinant dog gastric lipase, rDGL) in the time course of hydrolysis of prochiral triolein as a substrate. From the measurements of the diglyceride enantiomeric excess it was confirmed that PPL was not stereospecific (position sn-1 vs sn-3 of triolein), whereas MML and rDGL preferentially hydrolyzed the ester bond at position sn-1 and sn-3, respectively. The enantiomeric excess of DAGs was not constant with time, decreasing with the course of hydrolysis. This was due to the fact that DAGs can be products of the stereospecific hydrolysis of TAGs and substrates for stereospecific hydrolysis into monoacylglycerols.     

Stereoselective enzymatic hydrolysis of 2-cyclohexyl-and 2-phenyl-1,3-propanediol diacetate in biphasic systems

Summary A key intermediate (S(–) 2-cyclohexyl-1,3-propanediol monoacetate) was made with high optical purity for the total synthesis of a new angiotensin converting enzyme inhibitor, Fosinopril. The stereoselective hydrolysis of 2-cyclohexyl-1,3-propanediol diacetate (I) and 2-phenyl-1,3-propanediol diacetate (II) was carried out with lipases. Among various lipases evaluated, only porcine pancreatic lipase (PPL) and Chromobacterium viscosum lipase demonstrated efficient conversion and gave the desired enantiomer of monoacetate. In aqueous solution, the desired S(–) monoacetate exhibited an optical purity of 65%–80% (30%–60% enantiomeric excess [e.e.]). However, when the same reactions were conducted in a biphasic system, the product S(–) monoacetate exhibited an optical purity of 99%–100% (98%–100% e.e.). The high purity product was achieved with 65 mol% yield at 1% substrate concentration. Among various solvents evaluated in biphasic systems, efficient hydrolysis was achieved in toluene, cyclohexane, and trichloro-trifluoroethane. The crude PPL was partially purified and two lipase fractions (A and B) were identified. Lipases A and B had a molecular mass of 38 000 and 40 000 daltons, respectively, and both were found to catalyze the hydrolysis of I and II to the appropriate monoacetate in a biphasic system. Offprint requests to: R. N. Patel     

Determination of the quantitative stereoselectivity fingerprint of lipases during hydrolysis of a prochiral triacylglycerol

We propose a method for characterizing quantitatively the stereoselectivity of lipases during hydrolysis of triacylglycerols. Although it is of general applicability, we demonstrate it specifically for sn-1,3-regiospecific lipases. In this case the method generates a "stereoselectivity fingerprint" that consists of ratios of the specificity constants for the various reactions that produce and consume the 1,2-sn- and 2,3-sn-diacylglycerols. We use the method to determine the stereoselectivity fingerprint of several lipases during the hydrolysis of the prochiral substrate triolein. Our method opens up the possibility of correlating quantitative fingerprints with structural information, in the quest to elucidate the mechanisms underlying the stereoselectivity of lipases.     

A multisubstrate assay for lipases/esterases: Assessing acyl chain length selectivity by reverse-phase high-performance liquid chromatography

Lipases and esterases are hydrolytic enzymes and are known to hydrolyze esters with unique substrate specificity and acyl chain length selectivity. We have developed a simple competitive multiple substrate assay for determination of acyl chain length selectivity of lipases/esterases using RP-HPLC with UV detection. A method for separation and quantification of 4-nitrophenyl fatty acid esters (C₄–C₁₈) was developed and validated. The chain length selectivity of five lipases and two esterases was determined in a multisubstrate reaction system containing equimolar concentrations of 4-nitrophenyl esters (C₄–C₁₈). This assay is simple, reproducible, and a useful tool for determining chain length selectivity of lipases/esterases.     

Enzymatic hydrolysis of soybean oil using lipase from different sources to yield concentrated of polyunsaturated fatty acids

The ability of three commercially available lipases to mediate the hydrolysis of the soybean oil to yield concentrated of essential fatty acids was evaluated. The tested lipases were from microbial (Candida rugosa and Thermomyces lanuginosa) and animal cells (Porcine pancreatic lipase). In terms of free fatty acids, microbial lipases were more effective to promote the enzymatic hydrolysis of the soybean oil (over 70%) than the porcine pancreatic lipase (24%). In spite of this, porcine pancreatic lipase (PPL) showed the most satisfactory specificity towards both essential fatty acids and was, therefore, chosen to carry out additional studies. An experimental design was performed taking into consideration the enzyme and NaCl amounts as independent variables. The main effects were fitted by multiple regression analysis to a linear model and maximum fatty acids concentration could be obtained using 3.0 wt% of lipase and 0.08 wt% of NaCl. The mathematical model representing the hydrolysis degree was found to describe adequately the experimental results. Under these conditions, concentrations of 29.5 g/L and 4.6 g/L for linoleic and linolenic acids, respectively, were obtained.     

Candida rugosa lipase encapsulated with magnetic sporopollenin: design and enantioselective hydrolysis of racemic arylpropanoic acid esters

Abstract

The aim of this study was to prepare the encapsulation of Candida rugosa lipase (CRL) with magnetic sporopollenin. The sporopollenin was covalent immobilized onto magnetic nanoparticles (Fe₃O₄), grafted amino (APTES), or epoxy groups (EPPTMS). CRL was sol-gel encapsulated in the presence of magnetic sporopollenin/Fe₃O₄ nanoparticles. The influence of activation agents ([3-(2,3-epoxypropoxy) propyl] trimethoxysilane (EPPTMS), (3-Aminopropyl)triethoxysilane (APTES) and pH and thermal stabilities of the biocatalyst were assessed. Experimental data showed the improved catalytic activity at different pH and temperature values. At 60?°C, free lipase lost its initial activity within 80?min of time, although the encapsulated lipases retained their initial activities of about 65% by APTES and 60% by EPPTMS after 120?min of heat treatment at 60?°C. The catalytic properties of the encapsulated lipases were utilized to hydrolysis of racemic aromatic carboxylic acid methyl esters (Naproxen and 2-phenoxypropionic acid). The results show that the sporopollenin-based encapsulated lipase (Fe-A-Spo-E) has greater enantioselectivity and conversion in comparison with the encapsulated lipase without supports (lipase-enc).     

Improvement of lipase obtaining system by orange waste-based solid-state fermentation: production,characterization and application

Abstract

Lipases are an economic important group of biocatalysts that can be produced by some fungal under solid-state fermentation. Orange wastes are source of lipases and potential substrates for lipases production. This work assessed 19 fugal strains cultivated in Citrus sinensis cv. Hamlin orange wastes (peel, frit and core) for production of lipases in order to generate compounds with antioxidant, antimicrobial and cytotoxic properties. Fifteen of those fungi grew and produced lipases, mainly the Aspergillus brasiliensis [National Institute of Quality Control (INCQS) 40036]/frit system, which showed 99.58?U/g total lipase. The substrate with the highest production of lipase was frit with 26.67 and 78.91?U/g of total lipases produced on average by the 15 microorganisms. Aspergillus niger 01/frit (33.53?U/g) and Aspergillus niger (INCQS 40015)/frit (34.76?U/g) systems showed the highest specificity values in all the herein tested synthetic substrates with 4, 12 and 16 carbons. Analysis of the fatty acid profile of hydrolysis products obtained in the most prominent systems applied to corn and sunflower oils showed: palmitic acid, linoleic acid, oleic acid, and stearic acid. These acids showed antioxidant capacity of up to 58% DPPH (2,2-diphenyl-1-pierylhydrazyl) radical reduction and antibacterial activity against Escherichia coli, Listeria monocytogenes, Pseudomonas aureginosa, Salmonella Enteritidis and Staphylococcus aureus, as well as cytotoxicity to SCC9 cells (squamous cancer cells).     

How Can a Yeast Catalyze Enantioselective Protonation?

In the enantioselective hydrolysis of enol esters with Pichia farinosa IAM 4682 to give α-chiral ketones, the final enantioselective protonation was found to be promoted by a factor differed from the enzyme catalyzing simple hydrolysis. The crude cell-free extracts from P. farinosa was subjected to ultracentrifugation. Although the supernatant fraction could hydrolyze 1-acetoxy-2-benzylcyclohexene (1), the resulting 2-benzylcyclohexanone (2) was a racemate. On the other hand, the precipitate could not hydrolyze 1. However, on mixing of both fractions the suspension recovered again an enantioselective ability effectively to afford optically active (R)-2. The same phenomena were observed in the hydrolysis using commercially available lipases and an esterase. These results indicate that enantioselectivity-promoting factor should be involved in the precipitate.     

Stereoselectivity of Mucorales lipases toward triradylglycerols--a simple solution to a complex problem

The lipases from Rhizopus and Rhizomucor are members of the family of Mucorales lipases. Although they display high sequence homology, their stereoselectivity toward triradylglycerols (sn-2 substituted triacylglycerols) varies. Four different triradylglycerols were investigated, which were classified into two groups: flexible substrates with rotatable O'-C1' ether or ester bonds adjacent to C2 of glycerol and rigid substrates with a rigid N'-C1' amide bond or a phenyl ring in sn-2. Although Rhizopus lipase shows opposite stereopreference for flexible and rigid substrates (hydrolysis in sn-1 and sn-3, respectively), Rhizomucor lipase hydrolyzes both groups of triradylglycerols preferably in sn-1. To explain these experimental observations, computer-aided molecular modeling was applied to study the molecular basis of stereoselectivity. A generalized model for both lipases of the Mucorales family highlights the residues mediating stereoselectivity: (1) L258, the C-terminal neighbor of the catalytic histidine, and (2) G266, which is located in a loop contacting the glycerol backbone of a bound substrate. Interactions with triradylglycerol substrates are dominated by van der Waals contacts. Stereoselectivity can be predicted by analyzing the value of a single substrate torsion angle that discriminates between sn-1 and sn-3 stereopreference for all substrates and lipases investigated here. This simple model can be easily applied in enzyme and substrate engineering to predict Mucorales lipase variants and synthetic substrates with desired stereoselectivity.     

Stereoselectivity of lipases. I. Hydrolysis of enantiomeric glyceride analogues by gastric and pancreatic lipases, a kinetic study using the monomolecular film technique

In the present study, porcine pancreatic lipase, rabbit gastric lipase, and human gastric lipase stereospecificity toward enantiomeric glyceride derivatives was kinetically investigated using the monomolecular film technique. Pseudoglycerides such as enantiomeric 1(3)-alkyl-2,3(1,2)-diacyl-sn-glycerol, enantiomeric 1(3)-alkyl-2-acyl-sn-glycerol, or enantiomeric 1(3)-acyl-2-acylamino-2-deoxy-sn-glycerol were synthesized in order to assess the lipase stereoselectivity during the hydrolysis of either the primary or the secondary ester position of these glycerides analogues. The cleaved acyl moiety was the same in both enantiomers, thereby excluding the possibility of effects occurring due to fatty acid specificity. We observed a porcine pancreatic lipase sn-3 stereoselectivity when using the enantiomeric 1(3)-alkyl-2-acylamino-2-deoxy-sn-glycerol (diglyceride analogue) which contrasted with the lack of stereoselectivity observed when using the enantiomeric 1(3)-alkyl-2,3(1,2)-diacyl-sn-glycerol (triglyceride analogue). The gastric lipases, in contrast to the pancreatic lipase, preferentially catalyze the hydrolysis of the primary sn-3 ester bond of the enantiomeric monoakyl-diacyl pair tested. From these kinetic data, high hydrolysis rates and no chiral discrimination were observed in the case of rabbit gastric lipase, whereas low rates and a clear chiral discrimination was noticed in the case of human gastric lipase during hydrolysis of the acyl chain from the secondary ester bond of 1(3)-alkyl-2-acyl enantiomers. It is particularly obvious that in the case of human gastric lipase decreasing the lipid packing increases the lipase sn-3 stereopreference during hydrolysis of the primary ester bond of the enantiomeric 2-acylamino derivatives (diglyceride analogue).     

Substrate specificity,regioselectivity and hydrolytic activity of lipases activated from Geotrichum sp.

Substrate specificity (typoselectivity), regioselectivity and hydrolytic activity of induced lipases from three strains (4012, 4013, 4166) of Geotrichum candidum and that of Geotrichum ludwigii (48) were investigated. The lipases were induced in two types of culture media, of which the medium containing peptone as nitrogen source was proved to give better results. Olive oil was employed as inductor for the lipase activity. Activated lipases represented mostly extracelullar lipases, which penetrated through cellular membrane into medium. The activity of cell-bound lipase was also determined. Most of lipases belong to the group of specific lipases able to hydrolyse ester bonds in the positions sn-1 and sn-3 ester of triacylglycerols (1,3-selective lipases) and display specificity to saturated fatty acids. All activated lipases from Geotrichum sp., extracellular and cell-bound, were used as biocatalyst in the blackcurrant oil hydrolysis.     

Inhibition of Incorporation of l-Alanine into Uridine-diphospho N-acetylmuramic Acid by Glycine

Lipases from Aspergillus niger and Rhizopus delemar hydrolyzed triolein and produced l,2 (2,3)-diolein and 2-monoolein. These two lipases appears to have strong specificity towards the outer chains of the triglyceride. Comparing the proportions of fatty acids in position 1 (3) of cocoa butter with proportions of fatty acids liberated after limited hydrolysis of cocoa butter, it becomes clear that these two lipases do not hydrolyze the ester bond in position 2 of the triglyceride.

On the other hand, lipases from Geotrichum candidum Link and Penicillium cyclopium Westring attacked the fatty acid chains regardless of their positions. Geotrichum candidum lipase liberated oleic acid and palmitic acid in preference to stearic acid from cocoa butter.     

Solvent tolerant Pseudomonads as a source of novel lipases for applications in non-aqueous systems

Abstract

Lipases (triacylglycerol acylhydrolases, EC 3.1.1.3) are ubiquitous biocatalysts known to catalyze the hydrolysis of water insoluble triglycerides in aqueous medium and carry out the reverse reaction (synthesis) under organic solvent rich medium. Microbial lipases have received a great deal of attention in the field of food technology, pharmaceutical sciences, chemical and detergent industries due to their stability, selectivity, mild operation conditions and broad substrate specificity. Despite these advantages, low activity and stability displayed in organic medium has restricted their commercial application in organic synthesis. Researchers have explored alternative ways to modify the enzymes making them suitable for use in non-conventional media. In this context, harvesting lipases from “Solvent Tolerant Microbes” has recently become an attractive approach. These microbes are able to grow in the presence of high concentrations of organic solvents, generally known to have detrimental effect on microorganisms. Such microbes survive through novel adaptation mechanisms and secretion of solvent stable enzymes having efficient functionality in solvent-rich media. These enzymes could be useful for bioconversion in non-conventional media. In the current review, this approach is described with an emphasis on characteristics, applications and genetic aspect of lipases from the genus Pseudomonas.     

Directed evolution of Bacillus licheniformis lipase for improvement of thermostability

Lipases catalyze the hydrolysis of carboxylic acid esters and owing to their vast substrate specificity, they have many industrial applications. Due to the demand of thermostable lipases in industrial applications, we have enhanced the thermostability of lipase from Bacillus licheniformis RSP-09. The thermostable mutant lipases of Bacillus licheniformis RSP-09 were isolated following two rounds of directed evolution using error-prone PCR. The best mutant lipases obtained after first and second round of error-prone PCR were purified and characterized. The mutant lipases showed increased thermostability and retained catalytic function. The best mutant lipase (eP-231-51) showed 13.5-fold increase in percentage thermal stability (% remaining activity after incubation of purified enzyme at 60 °C for 1 h) than wild-type lipase. Also, this mutant lipase (ep-231-51) showed 30% improved catalytic efficiency compared with the wild-type which is due to significant decrease in K_m and marginal increase in k_cat. In addition, the thermostable mutant lipases have shown resistance to hydrophobic organic solvents. The role of mutations in the best mutant lipases of second round i.e. eP-231-51 (Asp72Gly, Asp61Gly, Tyr129His, and Thr101Pro) and eP-231-137 (Leu49Arg, Thr101Pro, Asp72Gly), that led to thermostability have been postulated after the comparison of molecular models of wild-type and mutated enzymes.     

Morphological,biochemical and kinetic properties of lipase from Candida rugosa immobilized in zirconium phosphate

Zirconium phosphate (ZrP), a low-cost inorganic material with well-defined physicochemical properties, was successfully used as support for immobilizing Candida rugosa lipase by covalent bonding. The immobilized derivative showed high catalytic activity in both aqueous and non-aqueous media. Fourier transform infrared spectroscopy, X-ray diffraction, and scanning electron microscopy measurements demonstrated that the ZrP fulfilled the morphological requirements for use as a matrix for immobilizing lipases. The free and immobilized lipases were compared in terms of pH, temperature and thermal stability. The immobilized lipase had a higher pH optimum (7.5) and higher optimum temperature (50°C) than the free lipase. Immobilization also increased the thermal stability. The hydrolysis of p-nitrophenyl palmitate (pNPP) by immobilized lipase, examined at 37°C, followed Michaelis–Menten kinetics. Values for K_m=1.18 µM and V_max=325Umg^?1 indicated that the immobilized system was subject to mass transfer limitations. The immobilized derivative was also tested under repetitive reaction batches in both ester hydrolysis and synthesis.