Catalytic characterization of heterodimeric linoleate 13S-lipoxygenase from black soybean (Glycine max (L.) Merr.).

A novel lipoxygenase (BLOX) was purified from black soybean (Glycine max (L.) Merr.), and its catalytic properties were characterized. The molecular weight of BLOX was 101 kDa and its unique heterodimeric structure with two different subunits of molecular weight 46 kDa and 55 kDa was elucidated. The optimum pH and temperature of BLOX were pH 9.5 and 40 °C, respectively. BLOX was highly stable at the pH range of 6.0-10.0 and below 40 °C, and was stimulated by adding ferrous ion (Fe2+). In terms of substrate specificity, BLOX showed a substrate preference to linoleic acid that is the main substance to produce hydroperoxides in soybean. When it reacted with linoleic acid, the major product was 13(S)-hydroperoxy-9,11-octadecadienoic acid; therefore, it could be classified into the linoleate 13S-LOX family (EC 1.13.11.12). Finally, the kinetic parameters (Vmax, Km, and kcat) of BLOX were 0.124 mM min-1, 0.636 mM, and 12.28 s-1, respectively, and consequently, the catalytic efficiency (kcat/Km) was calculated as 1.93 × 104 M-1·s-1. These catalytic characteristics of BLOX could contribute to understanding the enzymatic rancidification of black soybean, and to further biotechnical approaches to control and mitigate the deterioration.

Purification and Product Characterization of Lipoxygenase from Opium Poppy Cultures (Papaver somniferum L.).

Opium poppy (Papaver somniferum L.) is an ancient medicinal plant producing pharmaceutically important benzylisoquinoline alkaloids. In the present work we focused on the study of enzyme lipoxygenase (LOX, EC 1.13.11.12) from opium poppy cultures. LOX is involved in lipid peroxidation and lipoxygenase oxidation products of polyunsaturated fatty acids have a significant role in regulation of growth, development and plant defense responses to biotic or abiotic stress. The purpose of this study was to isolate and characterize LOX enzyme from opium poppy callus cultures. LOX was purified by ammonium sulfate precipitation and then followed by hydrophobic chromatography using Phenyl-Sepharose CL-4B and hydroxyapatite chromatography using HA Ultrogel sorbent. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis and immunoblotting revealed that LOX from opium poppy cultures was a single monomeric protein showing the relative molecular weight of 83 kDa. To investigate the positional specificity of the LOX reaction, purified LOX was incubated with linoleic acid and the products were analyzed by high-performance liquid chromatography in two steps, firstly with reverse phase (120-5 Nucleosil C18 column) and secondly with normal phase (Zorbax Rx-SIL column). LOX converted linoleic acid primarily to 13-hydroperoxy-(9Z,11E)-octadecadienoic acids (78%) and to a lesser extent 9-hydroperoxy-(10E,12Z)-octadecadienoic acids (22%). Characterization of LOX from opium poppy cultures provided valuable information in understanding LOX involvement in regulation of signaling pathways leading to biosynthesis of secondary metabolites with significant biological activity.

Do lipoxygenases occur in viruses?: Expression and characterization of a viral lipoxygenase-like protein did not provide evidence for the existence of functional viral lipoxygenases.

Lipoxygenases are lipid peroxidizing enzymes, which frequently occur in higher plants and animals. In bacteria, these enzymes are rare and have been introduced via horizontal gene transfer. Since viruses function as horizontal gene transfer vectors and since lipoxygenases may be helpful for releasing assembled virus particles from host cells we explored whether these enzymes may actually occur in viruses. For this purpose we developed a four-step in silico screening strategy and searching the publically available viral genomes for lipoxygenase-like sequences we detected a single functional gene in the genome of a mimivirus infecting Acantamoeba polyphaga. The primary structure of this protein involved two putative metal ligand clusters but the recombinant enzyme did neither contain iron nor manganese. Most importantly, it did not exhibit lipoxygenase activity. These data suggests that this viral lipoxygenase-like sequence does not encode a functional lipoxygenase and that these enzymes do not occur in viruses.

Catalase-Related Allene Oxide Synthase, on a Biosynthetic Route to Fatty Acid Cyclopentenones: Expression and Assay of the Enzyme and Preparation of the 8R-HPETE Substrate.

Catalase-related allene oxide synthase (cAOS) is a hemoprotein that converts a specific fatty acid hydroperoxide to an unstable allene oxide intermediate at turnover rates in the order of 1000 per second. Fatty acid allene oxides are intermediates in the formation of cyclopentenone or hydrolytic products in marine systems, most notably the prostanoid-related clavulones. Although the key catalytic amino acid residues around the active site of cAOS are the same as in true catalases, cAOS does not react with hydrogen peroxide. cAOS occurs exclusively as the N-terminal domain of a naturally occurring fusion protein with a C-terminal lipoxygenase (LOX) domain that supplies the hydroperoxide substrate. In marine invertebrates, an 8R-LOX domain converts arachidonic acid to 8R-hydroperoxyeicosatetraenoic acid (8R-HPETE) and the cAOS domain forms an 8,9-epoxy allene oxide. The fusion protein from the sea whip octocoral Plexaura homomalla is the prototypical model with crystal structures of the individual domains. The cAOS (43kDa) expresses exceptionally well in Escherichia coli, with yields of up to 100mg/L. This article describes in detail expression and assay of the P. homomalla cAOS and two methods for the preparation of its 8R-HPETE substrate. Another article in this volume focuses on the P. homomalla 8R-LOX (Gilbert, Neau, & Newcomer, 2018).

Soy flour as an alternative to purified lipoxygenase for the enzymatic synthesis of resolvin analogues.

Specialized pro-resolving mediators are lipid signaling molecules synthesized from omega-3 and -6 polyunsaturated fatty acids, which promote the resolution of the inflammatory response. They are potential drug targets for the treatment of numerous conditions linked with uncontrolled inflammation. Many of these mediators can be effectively synthesized using enzymes, such as lipoxygenases. However, these enzymes are expensive to purchase and can be difficult to isolate. In this work, we show that commercial soy flour can be used directly as a source of lipoxygenase for the biosynthesis of specialized pro-resolving mediators from DHA and other biologically important fatty acids. The reaction was optimized and the products characterized. We found that the reaction yield and products were comparable to those synthesized using a commercial 15-lipoxygenase preparation.

Expression, purification, and characterization of a novel acidic Lipoxygenase from Myxococcus xanthus.

The gene encoding a novel acidic lipoxygenase from Myxococcus xanthus DK1622 (accession: WP_011551853.1) was cloned into vector pET-28a and expressed in Escherichia coli BL21(DE3). The recombinant enzyme (rMxLOX), with a molecular weight of approximately 80 kDa, was purified to homogeneity using one-step nickel-affinity chromatography and showed an activity of 5.6 × 104 U/mg. The optimum pH and temperature for rMxLOX activity were found to be 3.0 and 30 °C, respectively. Purified rMxLOX exhibited activity towards linoleic acid and arachidonic acid as substrates, with linoleic acid being the better substrate (Km and kcat values of 0.048 mM and 13.3/s, respectively). The synthetic dye aniline blue was decolorized 69.7 ± 3.5%, following incubation with rMxLOX for 35 min. These results reveal the potential for the use of rMxLOX in the pulp, textile, and wastewater treatment industries.

Defense-related Proteins from Chelidonium majus L. as Important Components of its Latex.

The aim of this review is to cover most recent research on plant pathogenesis- and defenserelated proteins from latex-bearing medicinal plant Chelidonium majus (Papaveraceae) in the context of its importance for latex activity, function, pharmacological activities, and antiviral medicinal use. These results are compared with other latex-bearing plant species and recent research on proteins and chemical compounds contained in their latex. This is the first review, which clearly summarizes pathogenesisrelated (PR) protein families in latex-bearing plants pointing into their possible functions. The possible antiviral function of the latex by naming the abundant proteins present therein is also emphasized. Finally latex-borne defense system is hypothesized to constitute a novel type of preformed immediate defense response against viral, but also non-viral pathogens, and herbivores.

13C ENDOR Spectroscopy of Lipoxygenase-Substrate Complexes Reveals the Structural Basis for C-H Activation by Tunneling.

In enzymatic C-H activation by hydrogen tunneling, reduced barrier width is important for efficient hydrogen wave function overlap during catalysis. For native enzymes displaying nonadiabatic tunneling, the dominant reactive hydrogen donor-acceptor distance (DAD) is typically ca. 2.7 Å, considerably shorter than normal van der Waals distances. Without a ground state substrate-bound structure for the prototypical nonadiabatic tunneling system, soybean lipoxygenase (SLO), it has remained unclear whether the requisite close tunneling distance occurs through an unusual ground state active site arrangement or by thermally sampling conformational substates. Herein, we introduce Mn2+ as a spin-probe surrogate for the SLO Fe ion; X-ray diffraction shows Mn-SLO is structurally faithful to the native enzyme. 13C ENDOR then reveals the locations of 13C10 and reactive 13C11 of linoleic acid relative to the metal; 1H ENDOR and molecular dynamics simulations of the fully solvated SLO model using ENDOR-derived restraints give additional metrical information. The resulting three-dimensional representation of the SLO active site ground state contains a reactive (a) conformer with hydrogen DAD of ∼3.1 Å, approximately van der Waals contact, plus an inactive (b) conformer with even longer DAD, establishing that stochastic conformational sampling is required to achieve reactive tunneling geometries. Tunneling-impaired SLO variants show increased DADs and variations in substrate positioning and rigidity, confirming previous kinetic and theoretical predictions of such behavior. Overall, this investigation highlights the (i) predictive power of nonadiabatic quantum treatments of proton-coupled electron transfer in SLO and (ii) sensitivity of ENDOR probes to test, detect, and corroborate kinetically predicted trends in active site reactivity and to reveal unexpected features of active site architecture.

2-Arylbenzo[b]furan derivatives as potent human lipoxygenase inhibitors.

Human lipoxygenases (LOXs) have been emerging as effective therapeutic targets for inflammatory diseases. In this study, we found that four natural 2-arylbenzo[b]furan derivatives isolated from Artocarpus heterophyllus exhibited potent inhibitory activities against human LOXs, including moracin C (1), artoindonesianin B-1 (2), moracin D (3), moracin M (4). In our in vitro experiments, compound 1 was identified as the most potent LOX inhibitor and the moderate subtype selective inhibitor of 12-LOX. Compounds 1 and 2 act as competitive inhibitors of LOXs. Moreover, 1 significantly inhibits LTB4 production and chemotactic capacity of neutrophils, and is capable of protecting vascular barrier from plasma leakage in vivo. In addition, the preliminary structure-activity relationship analysis was performed based on the above four naturally occurring (1-4) and six additional synthetic 2-arylbenzo[b]furan derivatives. Taken together, these 2-arylbenzo[b]furan derivatives, as LOXs inhibitors, could represent valuable leads for the future development of therapeutic agents for inflammatory diseases.

Evaluation of Olive Fruit Lipoxygenase Extraction Protocols on 9- and 13-Z,E-HPODE Formation.

In plant tissues, enzymes implicated in the lipoxygenase (LOX) pathway are responsible for the hydroperoxydation of polyunsaturated fatty acids, ultimately leading to the production of small chemical species involved in several physiological processes. During industrial olive oil production, these enzymes are activated upon crushing and grinding of olive fruit tissue, subsequently leading to the synthesis of volatile compounds responsible for the positive aroma and flavor of the oil. An investigation of LOX activity during olive fruit ripening and malaxation could assist in the production of oils with favorable aroma and taste. Therefore, a reliable method for olive LOX purification is crucial. Here we report a critical review of six LOX extraction protocols, two of which have shown minimum enzyme activity, possibly leading to misconceptions in the interpretation of experimental data. Future research concerning olive LOX should employ extraction methods that preserve enzyme activity.

Purification and properties of lipoxygenase from wheat seedlings infected by Fusarium graminearum and treated by salicylic acid.

Lipoxygenase from wheat seedlings in normal conditions, infected by Fusarium graminearum and treated by salicylic acid was isolated. The isolated enzyme was purified by the methods of salting-out (60% ammonium sulphate), dialysis, gel-filtration and ion-exchange chromatography. Specific activity of the purified enzyme was 8.0-12.5 ΔЕ234/mg of protein, degree of purification ­ 11.6-15.3 times. The enzyme yield was 18.3-27.9%. Molecular mass of lipoxygenase is 90 kDa, amino acid composition is distinguished by a high content of glutamic acid, proline, valine, isoleucine, leucine and low level of histidine, tyrosine, phenylalanine, threonine, tryptophan, cystein. Research of lipoxygenase substrate dependence indicated that the enzyme catalysed with the maximum velocity of the reaction of arachidonic acid oxidation at a substrate concentration of 4.5 mM at pH 7.2, the reaction of linoleic acid oxidation at a substrate concentration of 4.5 mM at pH 7.2 and the reaction of linolenic acid oxidation at a substrate concentration of 9.0 mM at pH 8.0. The change of wheat lipoxygenase activity depending on genotype resistance to Fusarium graminearum and millieu of germination was shown. One of the manifestations of the protective effect of salicylic acid is its ability to induce changes of lipoxygenase activity.

Expression and characterization of manganese lipoxygenase of the rice blast fungus reveals prominent sequential lipoxygenation of α-linolenic acid.

Magnaporthe oryzae causes rice blast disease and has become a model organism of fungal infections. M. oryzae can oxygenate fatty acids by 7,8-linoleate diol synthase, 10R-dioxygenase-epoxy alcohol synthase, and by a putative manganese lipoxygenase (Mo-MnLOX). The latter two are transcribed during infection. The open reading frame of Mo-MnLOX was deduced from genome and cDNA analysis. Recombinant Mo-MnLOX was expressed in Pichia pastoris and purified to homogeneity. The enzyme contained protein-bound Mn and oxidized 18:2n-6 and 18:3n-3 to 9S-, 11-, and 13R-hydroperoxy metabolites by suprafacial hydrogen abstraction and oxygenation. The 11-hydroperoxides were subject to ß-fragmentation with formation of 9S- and 13R-hydroperoxy fatty acids. Oxygen consumption indicated apparent kcat values of 2.8 s(-1) (18:2n-6) and 3.9 s(-1) (18:3n-3), and UV analysis yielded apparent Km values of 8 and 12 µM, respectively, for biosynthesis of cis-trans conjugated metabolites. 9S-Hydroperoxy-10E,12Z,15Z-octadecatrienoic acid was rapidly further oxidized to a triene, 9S,16S-dihydroperoxy-10E,12Z,14E-octadecatrienoic acid. In conclusion, we have expressed, purified and characterized a new MnLOX from M. oryzae. The pathogen likely secretes Mo-MnLOX and phospholipases to generate oxylipins and to oxidize lipid membranes of rice cells and the cuticle.

Characterization of an omega-6 linoleate lipoxygenase from Burkholderia thailandensis and its application in the production of 13-hydroxyoctadecadienoic acid.

A recombinant putative lipoxygenase from Burkholderia thailandensis with a specific activity of 26.4 U mg(-1) was purified using HisTrap affinity chromatography. The native enzyme was a 75-kDa dimer with a molecular mass of 150 kDa. The enzyme activity and catalytic efficiency (k cat/K m) were the highest for linoleic acid (k cat of 93.7 s(-1) and K m of 41.5 µM), followed by arachidonic acid, α-linolenic acid, and γ-linolenic acid. The enzyme was identified as an omega-6 linoleate lipoxygenase (or a linoleate 13S-lipoxygenase) based on genetic and HPLC analyses as well as substrate specificity. The reaction conditions for the enzymatic production of 13-hydroxy-9,11(Z,E)-octadecadienoic acid (13-HODE) were optimal at pH 7.5, 25 °C, 20 g l(-1) linoleic acid, 2.5 g l(-1) enzyme, 0.1 mM Cu(2+), and 6% (v/v) methanol. Under these conditions, linoleate 13-lipoxygenase from B. thailandensis produced 20.8 g l(-1) 13-HODE (70.2 mM) from 20 g l(-1) linoleic acid (71.3 mM) for 120 min, with a molar conversion yield of 98.5% and productivity of 10.4 g l(-1) h(-1). The molar conversion yield and productivity of 13-HODE obtained using B. thailandensis lipoxygenase were 151 and 158% higher, respectively, than those obtained using commercial soybean lipoxygenase under the optimum conditions for each enzyme at the same concentrations of substrate and enzyme.

Adsorption induced denaturation: application to denaturation of soybean trypsin inhibitor (SBTI) and lipoxygenase (LOX) in soymilk.

Allyl glycidyl ether-ethylene glycol dimethacrylate copolymer with 25 % crosslink density has been functionalized with various amines. The polymer bearing a dibenzyl amino function efficiently removed the soybean trypsin inhibitor (SBTI) and lipoxygenase (LOX) from soymilk. The polymer binds SBTI and LOX efficiently (25-30 mg/g) through a combination of hydrophobic and ionic interactions and denatures them at room temperature by simple contact for 1 h. The bound proteins can be easily recovered almost quantitatively by elution with 1 % (v/v) acetic acid, and the polymer can be recycled at least 10 times without significant changes in binding capacity.

Purification, characterization and application of lipoxygenase isoenzymes from Lasiodiplodia theobromae.

Lipoxygenase oxidizes linoleic acid into hydroperoxy octadecadienoic acid (HPOD), which is important in food and flavour industries for production of bread and flavouring compounds. As Lasiodiplodia theobromae is an unexplored, good source of lipoxygenase, it was purified from it by size-exclusion (Sephadex G100) and ion-exchange (DEAE-cellulose) chromatography and characterized. Upon purification, L. theobromae was found to contain two different lipoxygenases, one of 93 kDa (LOX1) and another of 45 kDa (LOX2). Both the isoenzymes were having optimum pH 6.0 and optimum temperatures 50 and 40 °C, respectively. The catalytic efficiency of LOX1 and LOX2 was found to be 1300 and 1.67 × 10(9), respectively. The catalytic efficiency of LOX2 is higher than the catalytic efficiency of soya bean LOX1 that is 10.9 × 10(6). Both the isoenzymes of LOX oxidized linoleic acid to produce 9-HPOD and 13-HPOD both; however, LOX1 produced more of 9-HPOD and LOX2 produced more of 13-HPOD. Both the LOXes were not inhibited by jasmonic acid. Addition of LOX1 and LOX2 altered the elasticity as well as viscosity of dough prepared from bleached wheat flour.

Isolation and characterization of wild-type lipoxygenase LOX(Psa)1 from Pleurotus sapidus.

The lipoxygenase LOX(Psa) 1 of Pleurotus sapidus, originally investigated because of its ability to oxidize (+)-valencene to the valuable grapefruit aroma (+)-nootkatone, was isolated from the peptidase-rich lyophilisate using a three-step purification scheme including preparative isoelectric focusing and chromatographic techniques. Nano-liquid chromatography electrospray ionization tandem mass spectrometry (nLC-ESI-MS/MS) of the purified enzyme and peptide mass fingerprint analysis gave 38 peptides of the lipoxygenase from P. sapidus. Nearly 50% of the 643 amino acids long sequence encoded by the cDNA was covered. Both terminal peptides of the native LOX(Psa) 1 were identified by de novo sequencing, and the postulated molecular mass of 72.5 kDa was confirmed. With linoleic acid as the substrate, the LOX(Psa)1 showed a specific activity of 113 U mg(-1) and maximal activity at pH 7.0 and 30 degrees C, respectively.

Expression of soluble recombinant lipoxygenase from Pleurotus sapidus in Pichia pastoris.

The first heterologous expression of an iron-containing lipoxygenase from a basidiomycete in Pichia pastoris is reported. Five different expression constructs of the lipoxygenase gene LOX1 from Pleurotus sapidus were cloned and successfully transferred into P. pastoris SMD1168, but only one pPIC9K vector construct was functionally expressed. In this construct the vector-provided α-factor signal sequence was replaced by insertion of a second Kozak sequence between the signal sequence and the LOX1 gene. His(+) transformants were screened for their level of resistance to geneticin (G418). Lox1 was expressed under different culture conditions and purified using the N-terminal His-tag. Relative enzyme activity increased significantly 48h after methanol induction and was highest with 2mll(-1) inducer. The recombinant enzyme showed an optimal lipoxygenase activity at pH 7 and 30-35°C and a vmax like the wild-type enzyme.

Molecular cloning, characterization and expression of lipoxygenase 2 (lox-2) isozyme from Indian soybean [Glycine max (L.) Merrill] cv. Pusa 16.

The consumption of soybean is limited worldwide, despite being highly nutritious and having versatile uses due to the presence of grassy, beany and rancid off-flavour. The lipoxygenase-2 (LOX-2) is the key enzyme responsible for the production of volatiles released from the beans, which cause off-flavour in soy products. In this study, a 2.6-kb full-length lox2 gene (NCBI accession No. JQ929619.1) was isolated and cloned from soybean (Glycine max L. Merril) cv. Pusa 16. The cloned cDNA sequence of lox2 gene showed the complete open reading frame (ORF) of a putative protein, having 866 amino acids with start codon present at the foremost position and stop codon at the end. The theoretical pI of predicted protein was 6.22. A hydropathy profile calculated from the amino acid sequence resembled those of dicot LOXs, suggesting conservation of the secondary structure of these enzymes. The LOX-2 showed conserved six Histidine residues within a span of 520 to 590 amino acid position, a signature element for the enzyme activity. The lox2 gene was expressed using pET vector in prokaryotic expression system. The recombinant LOX-2 protein was purified after induction with IPTG (isopentyl thiogalactoside). A prominent band of 97 kDa was observed, when affinity purified fractions were analyzed by SDS-PAGE. The purified protein was characterized for the enzyme activity, substrate preference and K(m). Inhibitor studies with natural antioxidant molecules present in soybean revealed alpha-tocopherol to be the most effective inhibitor of LOX-2.

Molecular characterization of a lipoxygenase from the basidiomycete mushroom Pleurotus ostreatus.

The full-length cDNA of the gene PoLOX1 encoding a lipoxygenase (LOX) and its corresponding genomic DNA were isolated from the basidiomycete mushroom Pleurotus ostreatus strain H1. The deduced amino acid sequence of PoLOX1 showed similarity to a valencene dioxygenase of Pleurotus sapidus, putative LOX-like proteins from ascomycete, basidiomycete, and deuteromycete fungi, and known LOXs from plants, animals, and bacteria. PoLOX1 also contained the LOX iron-binding catalytic domain in the C-terminal region, but not the polycystin-1, lipoxygenase, alpha-toxin (PLAT) domain, which is usually found in the N-terminal region of eukaryotic LOXs. Genomic sequence analysis revealed that PoLOX1 was interrupted by one intron, and that the promoter region included TATA and CAAT boxes. Southern blot analysis indicated that PoLOX1 is a member of a small gene family comprising highly similar genes. Northern blot analysis revealed that it is transcribed more abundantly in the stipes of the fruit bodies than in the caps.

Overproduction, purification, and characterization of extracellular lipoxygenase of Pseudomonas aeruginosa in Escherichia coli.

Lipoxygenase (LOX; EC 1.13.11.12,) is an enzyme that is widely used in food industry to improve aroma, rheological, or baking properties of foods. In this study, we described the expression and characterization of Pseudomonas aeruginosa LOX in Escherichia coli. The recombinant LOX was successfully expressed and secreted by E. coli using its endogenous signal peptide. When induced with 1 mM isopropyl ß-D-1-thiogalactopyranoside (final concentration) at 20 °C for 47 h, the titer of the recombinant enzyme reached 3.89 U/mL. In order to characterize the catalytic properties, the recombinant LOX was purified to homogeneity on Q High Performance and Mono Q5/50GL sequentially. The molecular weight of the LOX was estimated as 70 kDa by sodium dodecyl sulfate polyacrylamide gel electrophoresis. The Km and Vmax of the recombinant enzyme were 48.9 µM and 0.226 µmol/min, respectively. The purified enzyme exhibited a maximum activity at 25 °C and pH 7.5. High-performance liquid chromatography analysis of the linoleic acid hydroperoxides produced by recombinant LOX revealed that the LOX from P. aeruginosa falls into linoleic acid 13(S)-LOX. To the best of our knowledge, this is the first report on the overexpression of extracellular LOX in microorganisms, and the achieved LOX yield is the highest ever reported.