The formation of 1-octen-3-ol from the 10-hydroperoxide isomer of linoleic acid by a hydroperoxide lyase in mushrooms (Psalliota bispora)

Genomic analysis of the hydrocarbon-producing, cellulolytic, endophytic fungus Ascocoryne sarcoides

The microbial conversion of solid cellulosic biomass to liquid biofuels may provide a renewable energy source for transportation fuels. Endophytes represent a promising group of organisms, as they are a mostly untapped reservoir of metabolic diversity. They are often able to degrade cellulose, and they can produce an extraordinary diversity of metabolites. The filamentous fungal endophyte Ascocoryne sarcoides was shown to produce potential-biofuel metabolites when grown on a cellulose-based medium; however, the genetic pathways needed for this production are unknown and the lack of genetic tools makes traditional reverse genetics difficult. We present the genomic characterization of A. sarcoides and use transcriptomic and metabolomic data to describe the genes involved in cellulose degradation and to provide hypotheses for the biofuel production pathways. In total, almost 80 biosynthetic clusters were identified, including several previously found only in plants. Additionally, many transcriptionally active regions outside of genes showed condition-specific expression, offering more evidence for the role of long non-coding RNA in gene regulation. This is one of the highest quality fungal genomes and, to our knowledge, the only thoroughly annotated and transcriptionally profiled fungal endophyte genome currently available. The analyses and datasets contribute to the study of cellulose degradation and biofuel production and provide the genomic foundation for the study of a model endophyte system.

A renewable source of energy is a pressing global need. The biological conversion of lignocellulose to biofuels by microorganisms presents a promising avenue, but few organisms have been studied thoroughly enough to develop the genetic tools necessary for rigorous experimentation. The filamentous-fungal endophyte A. sarcoides produces metabolites when grown on a cellulose-based medium that include eight-carbon volatile organic compounds, which are potential biofuel targets. Here we use broadly applicable methods including genomics, transcriptomics, and metabolomics to explore the biofuel production of A. sarcoides. These data were used to assemble the genome into 16 scaffolds, to thoroughly annotate the cellulose-degradation machinery, and to make predictions for the production pathway for the eight-carbon volatiles. Extremely high expression of the gene swollenin when grown on cellulose highlights the importance of accessory proteins in addition to the enzymes that catalyze the breakdown of the polymers. Correlation of the production of the eight-carbon biofuel-like metabolites with the expression of lipoxygenase pathway genes suggests the catabolism of linoleic acid as the mechanism of eight-carbon compound production. This is the first fungal genome to be sequenced in the family Helotiaceae, and A. sarcoides was isolated as an endophyte, making this work also potentially useful in fungal systematics and the study of plant–fungus relationships.

Oxylipins in fungi

In nearly every living organism, metabolites derived from lipid peroxidation, the so-called oxylipins, are involved in regulating developmental processes as well as environmental responses. Among these bioactive lipids, the mammalian and plant oxylipins are the best characterized, and much information about their physiological role and biosynthetic pathways has accumulated during recent years. Although the occurrence of oxylipins and enzymes involved in their biosynthesis has been studied for nearly three decades, knowledge about fungal oxylipins is still scarce as compared with the situation in plants and mammals. However, the research performed so far has shown that the structural diversity of oxylipins produced by fungi is high and, furthermore, that the enzymes involved in oxylipin metabolism are diverse and often exhibit unusual catalytic activities. The aim of this review is to present a synopsis of the oxylipins identified so far in fungi and the enzymes involved in their biosynthesis.

PpoC from Aspergillus nidulans is a fusion protein with only one active haem

In Aspergillus nidulans Ppos [psi (precocious sexual inducer)-producing oxygenases] are required for the production of so-called psi factors, compounds that control the balance between the sexual and asexual life cycle of the fungus. The genome of A. nidulans harbours three different ppo genes: ppoA, ppoB and ppoC. For all three enzymes two different haem-containing domains are predicted: a fatty acid haem peroxidase/dioxygenase domain in the N-terminal region and a P450 haem-thiolate domain in the C-terminal region. Whereas PpoA was shown to use both haem domains for its bifunctional catalytic activity (linoleic acid 8-dioxygenation and 8-hydroperoxide isomerization), we found that PpoC apparently only harbours a functional haem peroxidase/dioxygenase domain. Consequently, we observed that PpoC catalyses mainly the dioxygenation of linoleic acid (18:2Delta9Z,12Z), yielding 10-HPODE (10-hydroperoxyoctadecadienoic acid). No isomerase activity was detected. Additionally, 10-HPODE was converted at lower rates into 10-KODE (10-keto-octadecadienoic acid) and 10-HODE (10-hydroxyoctadecadienoic acid). In parallel, decomposition of 10-HPODE into 10-ODA (10-octadecynoic acid) and volatile C-8 alcohols that are, among other things, responsible for the characteristic mushroom flavour. Besides these principle differences we also found that PpoA and PpoC can convert 8-HPODE and 10-HPODE into the respective epoxy alcohols: 12,13-epoxy-8-HOME (where HOME is hydroxyoctadecenoic acid) and 12,13-epoxy-10-HOME. By using site-directed mutagenesis we demonstrated that both enzymes share a similar mechanism for the oxidation of 18:2Delta9Z,12Z; they both use a conserved tyrosine residue for catalysis and the directed oxygenation at the C-8 and C-10 is most likely controlled by conserved valine/leucine residues in the dioxygenase domain.

Influence of sporophore development, damage, storage, and tissue specificity on the enzymic formation of volatiles in mushrooms (Agaricus bisporus)

The enzymic oxidation of the polyunsaturated fatty acid-linoleic acid leads, in fungi, to the formation of a unique class of nonconjugated hydroperoxides, which are cleaved to form eight-carbon volatiles characteristic of mushroom and fungal flavor. However, the enzymes involved in this biosynthetic pathway, the bioavailability of the fatty acid substrate, and the occurrence of the reaction products (hydroperoxides and eight-carbon volatiles) are not fully understood. This study investigated the lipids, fatty acids, and hydroperoxide levels, as well as eight-carbon volatile variations in the fungal model Agaricus bisporus, according to four parameters: sporophore development, postharvest storage, tissue type, and damage. Eight-carbon volatiles were measured using solid phase microextraction and gas chromatography-mass spectrometry. Tissue disruption had a major impact on the volatile profile, both qualitatively and quantitatively; 3-octanone was identified as the main eight-carbon volatile in whole and sliced sporophore, an observation overlooked in previous studies due to the use of tissue disruption and solvent extraction for analysis. Fatty acid oxidation and eight-carbon volatile emissions decreased with sporophore development and storage, and differed according to tissue type. The release of 1-octen-3-ol and 3-octanone by incubation of sporophore tissue homogenate with free linoleic acid was inhibited by acetylsalicylic acid, providing evidence for the involvement of a heme-dioxygenase in eight-carbon volatile production.

Identification of dioxygenases required for Aspergillus development. Studies of products, stereochemistry, and the reaction mechanism

Aspergillus sp. contain ppoA, ppoB, and ppoC genes, which code for fatty acid oxygenases with homology to fungal linoleate 7,8-diol synthases (7,8-LDS) and cyclooxygenases. Our objective was to identify these enzymes, as ppo gene replacements show critical developmental aberrancies in sporulation and pathogenicity in the human pathogen Aspergillus fumigatus and the genetic model Aspergillus nidulans. The PpoAs of A. fumigatus and A. nidulans were identified as (8R)-dioxygenases with hydroperoxide isomerase activity, designated 5,8-LDS. 5,8-LDS transformed 18:2n-6 to (8R)-hydroperoxyoctadecadienoic acid ((8R)-HPODE) and (5S,8R)-dihydroxy-9Z,12Z-octadecadienoic acid ((5S,8R)-DiHODE). We also detected 8,11-LDS in A. fumigatus and (10R)-dioxygenases in both Aspergilli. The diol synthases oxidized [(8R)-(2)H]18:2n-6 to (8R)-HPODE with retention of the deuterium label, suggesting antarafacial hydrogen abstraction and insertion of molecular oxygen. Experiments with stereospecifically deuterated 18:2n-6 showed that (8R)-HPODE was isomerized by 5,8- and 8,11-LDS to (5S,8R)-DiHODE and to (8R,11S)-dihydroxy-9Z,12Z-octadecadienoic acid, respectively, by suprafacial hydrogen abstraction and oxygen insertion at C-5 and C-11. PpoCs were identified as (10R)-dioxygenases, which catalyzed abstraction of the pro-S hydrogen at C-8 of 18:2n-6, double bond migration, and antafacial insertion of molecular oxygen with formation of (10R)-hydroxy-8E,12Z-hydroperoxyoctadecadienoic acid ((10R)-HPODE). Deletion of ppoA led to prominent reduction of (8R)-H(P)ODE and complete loss of (5S,8R)-DiHODE biosynthesis, whereas biosynthesis of (10R)-HPODE was unaffected. Deletion of ppoC caused biosynthesis of traces of racemic 10-HODE but did not affect the biosynthesis of other oxylipins. We conclude that ppoA of Aspergillus sp. may code for 5,8-LDS with catalytic similarities to 7,8-LDS and ppoC for linoleate (10R)-dioxygenases. Identification of these oxygenases and their products will provide tools for analyzing the biological impact of oxylipin biosynthesis in Aspergilli.

Steric analysis of 8-hydroxy- and 10-hydroxyoctadecadienoic acids and dihydroxyoctadecadienoic acids formed from 8R-hydroperoxyoctadecadienoic acid by hydroperoxide isomerases

8-Hydroxyoctadeca-9Z,12Z-dienoic acid (8-HODE) and 10-hydroxyoctadeca-8E,12Z-octadecadienoic acid (10-HODE) are produced by fungi, e.g., 8R-HODE by Gaeumannomyces graminis (take-all of wheat) and Aspergillus nidulans, 10S-HODE by Lentinula edodes, and 10R-HODE by Epichloe typhina. Racemic [8-(2)H]8-HODE and [10-(2)H]10-HODE were prepared by oxidation of 8- and 10-HODE to keto fatty acids by Dess-Martin periodinane followed by reduction to hydroxy fatty acids with NaB(2)H(4). The hydroxy fatty acids were analyzed by chiral phase high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) with 8R-HODE and 10S-HODE as standards. 8R-HODE eluted after 8S-HODE on silica with cellulose tribenzoate (Chiralcel OB-H), and 10S-HODE eluted before 10R-HODE on silica with an aromatic chiral selector (Reprosil Chiral-NR). 5S,8R-Dihydroxyoctadeca-9Z,12Z-dienoic acid (5S,8R-DiHODE) is formed from 18:2n-6 by A. nidulans and 8R,11S-dihydroxyoctadeca-9Z,12Z-dienoic acid (8R,11S-DiHODE) by Agaricus bisporus. 8R-Hydroperoxylinoleic acid (8R-HPODE) can be transformed to 5S,8R-DiHODE and 8R,11-DiHODE by Aspergillus spp., and 8R,13-dihydroxy-9Z,11E-dienoic acid (8R,13-DiHODE) can also be detected. We prepared racemic [5,8-(2)H(2)]5,8- and [8,11-(2)H(2)]8,11-DiHODE by oxidation and reduction as above and 8R,13S- and 8R,13R-DiHODE by oxidation of 8R-HODE by S and R lipoxygenases. The diastereoisomers were separated and identified by normal phase HPLC-MS/MS analysis. We used the methods for steric analysis of fungal oxylipins. Aspergillus spp. produced 8R-HODE (>95% R), 10R-HODE (>70% R), and 5S,8R- and 8R,11S-DiHODE with high stereoselectivity (>95%), whereas 8R,13-DiHODE was likely formed by nonenzymatic hydrolysis of 8R,11S-DiHODE.

Stereochemical correlation between 10-hydroperoxyoctadecadienoic acid and 1-octen-3-ol in Lentinula edodes and Tricholoma matsutake mushrooms

Linoleic acid (LA) incubated with a homogenate of Lentinula edodes or Tricholoma matsutake mushroom significantly increased the amount of (R)-1-octen-3-ol. The alcohol was identified as (S)-10-HODE with 90-87% and >99% enantiomeric excess (ee), respectively. During the incubation of LA with these homogenates in the presence of glutathione-glutathione peroxidase (GSH-GPx), which can reduce hydroperoxy fatty acids to the corresponding hydroxy acids, the formation of (R)-1-octen-3-ol was significantly inhibited, whereas the amount of 10-hydroxy-(8E,12Z)-8,12-octadecadienoic acid (10-HODE) was significantly increased. The acid was identified as (S)-10-HODE with 92-88% ee and >99% ee, respectively. The decrease in the amount of alcohol was approximately the same as the increase in amount of HODE in both mushrooms. These results indicate a stereochemical correlation between (R)-1-octen-3-ol and (S)-10-hydroperoxy-(8E,12Z)-8,12-octadecadienoic acid [(S)-10-HPODE] in both mushrooms.

Conversion of linoleic acid into novel oxylipins by the mushroom Agaricus bisporus

Oxylipins are associated with important processes of the fungal life cycle, such as spore formation. Here, we report the formation of FA metabolites in Agaricus bisporus. Incubation of a crude extract of lamellae with linoleic acid (18:2) led to the extensive formation of two oxylipins. They were identified as 8(R)-hydroxy-9Z,12Z-octadecadienoic acid (8-HOD) and 8(R),11 (S)-dihydroxy-9Z,12Z-octadecadienoic acid (8,11-diHOD) by using RP-HPLC, GC-MS, IR, GC-MS analysis of diastereomeric derivatives, and 1H NMR and 13C NMR spectroscopy. Neither compound has been reported before in A. bisporus. Oleic (18:1), alpha-linolenic (18:3n-3), and gamma-linolenic (18:3n-6) acids were converted into their 8-hydroxy derivatives as well, and 18:3n-3 was further metabolized to its 8,11-diol derivative. Reactions with [U-13C]18:2 demonstrated that the compounds 8-HOD and 8,11-diHOD were formed from exogenously supplied 18:2. When [U-13C]8-HOD was supplied, it was not converted into 8,11-diHOD, indicating that it was not an intermediate in the formation of 8,11-diHOD. When a crude extract of A. bisporus was incubated under an atmosphere of 16O2/18O2, the two hydroxyl groups of 8,11-diHOD contained either two 180 atoms or two 60 atoms. Species that contained one of each isotope could not be detected. We propose that the formation of the 8,11-dihydroxy compounds occurs through either an 8,11-endoperoxy, an 8-peroxo free radical, or an 8-hydroperoxy intermediate. In the latter case, the reaction should be catalyzed by dioxygenase with novel specificity.

Linoleic acid 10-hydroperoxide as an intermediate during formation of 1-octen-3-ol from linoleic acid in Lentinus decadetes

In order to confirm the biosynthetic pathway to 1-octen-3-ol from linoleic acid, a crude enzyme solution was prepared from the edible mushroom, Lentinus decadetes. When the reaction was performed in the presence of glutathione peroxidase, which can reduce organic hydroperoxide to the corresponding hydroxide, the amount of 1-octen-3-ol formed from linoleic acid was decreased. At the same time, an accumulation of linoleic acid 10-hydroxide could be detected. The 10-hydroperoxide therefore seems to be an intermediate on the biosynthetic pathway.

Hydroperoxy-arachidonic acid mediated n-hexanal and (Z)-3- and (E)-2-nonenal formation in Laminaria angustata

In higher plants, C6 and C9 aldehydes are formed from C18 fatty acids, such as linoleic or linolenic acid, through formation of 13- and 9-hydroperoxides, followed by their stereospecific cleavage by fatty acid hydroperoxide lyases (HPL). Some marine algae can also form C6 and C9 aldehydes, but their precise biosynthetic pathway has not been elucidated fully. In this study, we show that Laminaria angustata, a brown alga, formed C6 and C9 aldehydes enzymatically. The alga forms C9 aldehydes exclusively from the C20 fatty acid, arachidonic acid, while C6 aldehydes are derived either from C18 or from C20 fatty acid. The intermediates in the biosynthetic pathway were trapped by using a glutathione/glutathione peroxidase system, and subjected to structural analyses. Formation of (S)-12-, and (S)-15-hydroperoxy arachidonic acids [12(S)HPETE and 15(S)HPETE] from arachidonic acid was confirmed by chiral HPLC analyses. These account respectively for C9 aldehyde and C6 aldehyde formation, respectively. The HPL that catalyzes formation of C9 aldehydes from 12(S)HPETE seems highly specific for hydroperoxides of C20 fatty acids.

Plant and fungal lipoxygenases

Lipoxygenases (LOX) are ubiquitous in plants, and some are important for resistance to pathogens. The soybean LOX (SLOX) remain the prototypes for studying lipoxygenation. The 3-D structures of SLOX-1 and -3 reveal an N-terminal beta-barrel and a C-terminal catalytic domain. The beta-barrel with 30 kDa of the N-terminal peptide chain of SLOX-1 can be separated from the catalytic domain (60 kDa), which is a functional lipoxygenase designated "mini-LOX." The 3-D structures have made it possible to predict and interpret effects of point mutations on catalytic parameters and on the substrate and position specificity and to identify the catalytic base as Fe3+-OH-. The first catalytic step, hydrogen abstraction at C-11 of linoleic acid by Fe3+-OH-, is associated with a very large isotope effect (20-80), which can be explained by the quantum-mechanical concept of hydrogen tunneling "through a 2-D potential barrier." The prosthetic iron of SLOX-3 can be extracted and the apoenzyme can incorporate Fe3+ and regain LOX activity. Plant LOX can be elicited by fungal pathogens. One fungal LOX has been cloned and characterized. It is secreted by the take-all fungus, and the enzyme may contribute to its detrimental actions on wheat roots. The primary structure of Mn-LOX shows that it belongs to the LOX gene family, the metal ligands appear to be homologous, and electron paramagnetic resonance (EPR) spectra suggest redox cycling between Mn2+ and Mn3+. The hypothetical catalytic base, Mn3+-OH-, abstracts the pro-S hydrogen at C-11, and molecular oxygen is inserted in a suprafacial way at C-11 and -13 in a 1:3 ratio. Mn-LOX catalyses the conversion of the 11S-hydroperoxide to 13R-hydroperoxylinoleic acid. Mn-LOX is a novel tool for studying lipoxygenation and plant-fungal interactions.

The homolytic and heterolytic fatty acid hydroperoxide lyase-like activities of hematin

Pentenols and pentene dimers are biosynthetized in plants by homolytic fatty acid hydroperoxide lyase (HPL) or HPL-like enzymes. It has been found that these compounds can modify the flavor of olive oil. Reactions between hematin and 13-hydroperoxyoctadecatrienoic acid resulted in the formation of the same compounds via a free radical reaction in which an alkoxyl radical derived from linolenic acid hydroperoxide undergoes a beta-scission. (Z)-3-Hexenal has also been detected as a minor product of the reaction. It is bioconversed from the same substrate in plants by heterolytic HPL. Thanks to the redox cycle of its central iron, hematin has both homolytic and heterolytic HPL-like activities.

Fatty acid hydroperoxide lyase: a plant cytochrome p450 enzyme involved in wound healing and pest resistance

Plants continuously have to defend themselves against life-threatening events such as drought, mechanical damage, temperature stress, and potential pathogens. Nowadays, more and more similarities between the defense mechanism of plants and that of animals are being discovered. In both cases, the lipoxygenase pathway plays an important role. In plants, products of this pathway are involved in wound healing, pest resistance, and signaling, or they have antimicrobial and antifungal activity. The first step in the lipoxygenase pathway is the reaction of linoleic or linolenic acids with molecular oxygen, catalyzed by the enzyme lipoxygenase. The hydroperoxy fatty acids thus formed are highly reactive and dangerous for the plant and therefore further metabolized by other enzymes such as allene oxide synthase, hydroperoxide lyase, peroxygenase, or divinyl ether synthase. Recently, these enzymes have been characterized as a special class of cytochrome P450 enzymes. Hydroperoxide lyases cleave the lipoxygenase products, resulting in the formation of omega-oxo acids and volatile C6- and C9-aldehydes and -alcohols. These compounds are major contributors to the characteristic "fresh green" odor of fruit and vegetables. They are widely used as food flavors, for example, to restore the freshness of food after sterilization processes. The low abundance of these compounds in nature and the high demand make it necessary to synthesize them on a large scale. Lipoxygenase and hydroperoxide lyase are suitable biocatalysts for the production of "natural" food flavors. In contrast to lipoxygenase, which has been extensively studied, little is yet known about hydroperoxide lyase. Hydroperoxide lyases from different organisms have been isolated, and a few genes have been published lately. However, the structure and reaction mechanism of this enzyme are still unclear. The identification of this enzyme as a cytochrome P450 sheds new light on its structure and possible reaction mechanism, whereas recombinant expression brings a biocatalytic application into sight.

Characterization of lipoxygenase oxidation products by high-performance liquid chromatography with electron impact-mass spectrometric detection

Lipoxygenase (LOX) is an enzyme that oxygenates polyunsaturated fatty acids to their corresponding hydroperoxy derivatives. For example, LOX found in plants produce the corresponding 13- and 9-hydroperoxide derivatives of linoleic acid (13-HPOD and 9-HPOD). Identification of the HPOD products is usually accomplished by using gas chromatography with mass spectrometric (MS) detection, which requires extensive derivatization of the thermally unstable hydroperoxy group. Here we report a high-performance liquid chromatographic method in combination with electron impact (EI)-MS detection that separates and characterizes the HPOD isomers generated by soybean LOX type I oxygenation of linoleic (LA) and linolenic acids as well as HPOD products produced by photosensitized oxidation of LA. The method does not required derivatization of the hydroxyperoxide group, and location of its position can be determined by the EI-MS fragmentation pattern. The method has been used for the analysis of HPOD produced by action of partially purified LOX from the micro-alga Chlorella pyrenoidosa on LA. The study suggests the presence of two LOX isozymes in the micro-alga that oxygenate LA to its 13-HPOD and 9-HPOD derivatives. Moreover, the 9-LOX isozyme under anaerobic conditions cleaves 13-HPOD to 13-oxo-tridecadienoic acid and pentane but does not cleave 9-HPOD.

10-Oxo-trans-8-decenoic acid (ODA): production, biological activities, and comparison with other hormone-like substances in Agaricus bisporus*

The few well-characterized fungal growth-regulating substances include 10-oxo-trans-8-decenoic acid (ODA) and hercynine. This report deals with production and tissue location of ODA. It also describes some biological activities of addition of ODA, hercynine, and cytokinins on growth and postharvest morphogenesis of Agaricus bisporus. Production of ODA in sporophore extracts was limited mainly by oxygen availability and the possible occurrence of a competitive metabolic pathway. Presumably synthesized within the stipe and skin tissues, ODA accumulated in the gills. Mycelium growth rate on a potato-based medium was significantly increased in the presence of ODA. Moreover, stipe lengthening was slightly stimulated by 10 or 100 µM ODA. Although these findings were similar to previous ones (Mau JL, Beelman RB, Ziegler GR. Phytochemistry 1992;31:4059-64), ODA appeared poorly active in our assays and mycelium growth on asparagine-glucose medium was strongly inhibited by 200 µM ODA. In contrast with cytokinins or hercynine, ODA did not speed up cap opening. Finally, tests carried out on animal cells suggested a dose-dependent cytotoxic effect of ODA.

Biosynthesis of R-(+)-octane-1,3-diol. Crucial role of beta-oxidation in the enantioselective generation of 1,3-diols in stored apples

The biosynthesis of R-octane-1,3-diol and R-5(Z)-octene-1,3-diol, two natural antimicrobial agents in apples and pears, was investigated in stored apples after application of [9,10,12,13-3H]linoleic acid, [9,10,12,13,15,16-3H]linolenic acid, [1-14C]linoleic acid, [U-14C]oleic acid, lipoxygenase-derived metabolites of [9,10,12,13-3H]linoleic acid, 13C18-labeled linoleic acid hydroperoxides, and 2H-labeled octanol derivatives. Analysis of the products and quantification of incorporation and labeling pattern were achieved by high-performance liquid chromatography-radiodetection, capillary gas chromatography (GC)-isotope ratio mass spectrometry, and GC-mass spectrometry analysis. Almost all the applied precursors were partly transformed into R-octane-1,3-diol. Linoleic acid derivatives, still containing the 12,13 cis double bond, and octanol derivatives oxy-functionalized at carbon 3 were the most efficient precursors of the 1,3-diol. The data imply that R-octane-1,3-diol is generated in stored apples in the course of the beta-oxidation from R-3-hydroxy-octanoyl-SCoA originating from 2-cis-octenoyl-SCoA by enoyl-CoA hydratase. In an analogous fashion, R-5(Z)-octene-1,3-diol is formed from the unsaturated intermediate.

Recent investigations into the lipoxygenase pathway of plants

The plant lipoxygenase (LOX) pathway is in many respects the equivalent of the 'arachidonic acid cascade' in animals. The LOX-catalyzed dioxygenation of the plant fatty acids, linoleic and linolenic acids, is followed by metabolism of the resulting fatty acid hydroperoxides by other enzymes. Although the physiological functions of the end-products do not appear to be fully defined at this time, hormonal and anti-fungal activities have been reported.

High-performance liquid chromatography of linoleic acid hydroperoxides and their corresponding alcohol derivatives

The four major hydroperoxides derived from autoxidation or lipoxygenase action on linoleic acid or on methyl linoleate and their corresponding alcohol derivatives are resolved by high-performance liquid chromatography on Zorbax SIL 3 micron particulate columns irrigated with hexane-diethyl ether-acetic acid mixtures. The four major linoleic acid hydroperoxides are interconverted at different rates in benzene or carbon tetrachloride solutions but are stable to storage under nitrogen at -70 degrees C for several months.