Mechanisms in anti-inflammation and resolution: the role of lipoxins and aspirin-triggered lipoxins

Multicellular host responses to infection, injury or inflammatory stimuli lead to the formation of a broad range of chemical mediators by the host. The integrated response of the host is essential to health and disease; thus it is important to achieve a more complete understanding of the molecular and cellular events governing the formation and actions of endogenous mediators of resolution that appear to control the duration of inflammation. Lipoxins are trihydroxytetraene-containing lipid mediators that can be formed during cell-cell interactions and are predominantly counterregulators of some well-known mediators of inflammation. Since this circuit of lipoxin formation and action appears to be of physiological relevance for the resolution of inflammation, therapeutic modalities targeted at this system are likely to have fewer unwanted side effects than other candidates and current anti-inflammatory therapies. Here, we present an overview of the recent knowledge about the biosynthesis and bioactions of these anti-inflammatory lipid mediators.

Lipoxygenase is involved in the control of potato tuber development

Plant lipoxygenases (LOXs) are a functionally diverse class of dioxygenases implicated in physiological processes such as growth, senescence, and stress-related responses. LOXs incorporate oxygen into their fatty acid substrates and produce hydroperoxide fatty acids that are precursors of jasmonic acid and related compounds. Here, we report the involvement of the tuber-associated LOXs, designated the Lox1 class, in the control of tuber growth. RNA hybridization analysis showed that the accumulation of Lox1 class transcripts was restricted to developing tubers, stolons, and roots and that mRNA accumulation correlated positively with tuber initiation and growth. In situ hybridization showed that Lox1 class transcripts accumulated in the apical and subapical regions of the newly formed tuber, specifically in the vascular tissue of the perimedullary region, the site of the most active cell growth during tuber enlargement. Suppression mutants produced by expressing antisense coding sequence of a specific tuber LOX, designated POTLX-1, exhibited a significant reduction in LOX activity in stolons and tubers. The suppression of LOX activity correlated with reduced tuber yield, decreased average tuber size, and a disruption of tuber formation. Our results indicate that the pathway initiated by the expression of the Lox1 class genes of potato is involved in the regulation of tuber enlargement.

Lipoxygenase is involved in the control of potato tuber development

Plant lipoxygenases (LOXs) are a functionally diverse class of dioxygenases implicated in physiological processes such as growth, senescence, and stress-related responses. LOXs incorporate oxygen into their fatty acid substrates and produce hydroperoxide fatty acids that are precursors of jasmonic acid and related compounds. Here, we report the involvement of the tuber-associated LOXs, designated the Lox1 class, in the control of tuber growth. RNA hybridization analysis showed that the accumulation of Lox1 class transcripts was restricted to developing tubers, stolons, and roots and that mRNA accumulation correlated positively with tuber initiation and growth. In situ hybridization showed that Lox1 class transcripts accumulated in the apical and subapical regions of the newly formed tuber, specifically in the vascular tissue of the perimedullary region, the site of the most active cell growth during tuber enlargement. Suppression mutants produced by expressing antisense coding sequence of a specific tuber LOX, designated POTLX-1, exhibited a significant reduction in LOX activity in stolons and tubers. The suppression of LOX activity correlated with reduced tuber yield, decreased average tuber size, and a disruption of tuber formation. Our results indicate that the pathway initiated by the expression of the Lox1 class genes of potato is involved in the regulation of tuber enlargement.

Preferential induction of a 9-lipoxygenase by salt in salt-tolerant cells of Citrus sinensis L. Osbeck

Recent findings in our laboratory suggested that in citrus cells the salt induction of phospholipid hydroperoxide glutathione peroxidase, an enzyme active in cellular antioxidant defense, is mediated by the accumulation of hydroperoxides. Production of hydroperoxides occurs as a result of non-enzymatic auto-oxidation or via the action of lipoxygenases (LOXs). In an attempt to resolve the role of LOX activity in the accumulation of peroxides we analyzed the expression of this protein under stress conditions and in cells of Citrus sinensis L. differing in sensitivity to salt. Lipoxygenase expression was induced very rapidly only in the salt-tolerant cells and in a transient manner. The induction was specific to salt stress and did not occur with other osmotic-stress-inducing agents, such as polyethylene glycol or mannitol, or under hot or cold conditions, or in the presence of abscisic acid. The induction was eliminated by the antioxidants dithiothreitol and kaempferol, thus once more establishing a correlation between salt and oxidative stresses. Analyses of both in vitro and in vivo products of LOX revealed a specific 9-LOX activity, and a very fast reduction of the hydroperoxides to the corresponding hydroxy derivatives. This suggests that one of the metabolites further downstream in the reductase pathway may play a key role in triggering defense responses against salt stress.

A Phaseolus vulgaris lipoxygenase gene expressed in nodules and in Rhizobium tropici inoculated roots

A genomic clone encoding a common bean lipoxygenase (PvLOX5) was isolated from a Phaseolus vulgaris library. Reverse transcription-polymerase chain reaction analysis revealed that PvLOX5 is expressed during nodule development and in Rhizobium tropici inoculated roots. There was no detectable expression of PvLOX5 in non-inoculated roots, healthy leaves, leaves after Pseudomonas syringae pv. tabaci infection, floral buds or dry seeds.

Formation of 4-hydroxy-2-alkenals in barley leaves

In barley leaves 13-lipoxygenases are induced by jasmonates. This leads to induction of lipid peroxidation. Here we show by in vitro studies that these processes may further lead to autoxidative formation of (2E)-4-hydroxy-2-hexenal from (3Z)-hexenal.

Lipoxygenase isoforms in elicitor-treated parsley cell suspension cultures

Treatment of parsley cell cultures with a fungal elicitor triggered the induction of a lipoxygenase isoform which may be involved in the de novo synthesis of defence-response inducers, such as jasmonic acid or 12-oxo-phytodienoic acid.

A leaf lipoxygenase of potato induced specifically by pathogen infection

Lipoxygenase (LOX) activity has been identified consistently during pathogen-induced defense responses. Here we report the involvement of a specific leaf LOX gene of potato (Solanum tuberosum), designated POTLX-3 (GenBank/EMBL accession no. U60202), in defense responses against pathogens. The sequence of POTLX-3 does not match any other LOX genes of potato and has the greatest match to a tobacco LOX gene that contributes to a resistance mechanism against Phytophthora parasitica var nicotianae. POTLX-3 transcript accumulation was not detected in untreated, healthy potato organs or in wounded mature leaves. POTLX-3 mRNA accumulation was induced in potato leaves treated with ethylene or methyl jasmonate or infected with either virulent or avirulent strains of Phytophthora infestans, the causal agent of late blight. During the resistance response, POTLX-3 was induced within 6 hours, increased steadily through 24 hours, and its mRNA continued to accumulate for a week after inoculation. In contrast, when a plant was susceptible to P. infestans, induction of mRNA accumulation in response to inoculation was inconsistent and delayed. LOX activity assayed during an incompatible interaction in leaves peaked 3 days earlier than during a compatible interaction. POTLX-3 mRNA accumulation also was induced during hypersensitive response development caused by the incompatible pathogen Pseudomonas syringae pv phaseolicola. Our results show that POTLX-3 may be involved specifically in defense responses against pathogen infection.

Characterization of RCI-1, a chloroplastic rice lipoxygenase whose synthesis is induced by chemical plant resistance activators

A full-length lipoxygenase cDNA (RCI-1) has been cloned from rice (Oryza sativa) whose corresponding transcripts accumulate in response to treatment of the plants with chemical inducers of acquired resistance such as benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester (BTH), 2,6-dichloroisonicotinic acid (INA), and probenazole. In contrast, RCI-1 transcript levels did not increase after inoculation with compatible and incompatible races of the rice blast fungus Magnaporthe grisea and the nonhost pathogen Pseudomonas syringae pv. syringae. RCI-1 transcript levels also increased after exogenous application of jasmonic acid, but not upon wounding. Dose-response and time course experiments revealed a similar pattern of transcript accumulation and lipoxygenase activity in BTH-treated rice leaves. Enzymatic analysis of recombinant RCI-1 protein produced in Escherichia coli revealed that 13-hydroperoxy-octadecanoic acids were the predominant reaction products when either linoleic or linolenic acid used as a substrate. The RCI-1 sequence features a putative chloroplast targeting sequence at its N-terminus. Indeed, a protein consisting of the putative chloroplast transit peptide fused to green fluorescent protein was exclusively localized in chloroplasts, indicating that RCI-1 is a chloroplastic enzyme.

Herbivory-induced volatiles elicit defence genes in lima bean leaves

In response to herbivore damage, several plant species emit volatiles that attract natural predators of the attacking herbivores. Using spider mites (Tetranychus urticae) and predatory mites (Phytoseiulus persimilis), it has been shown that not only the attacked plant but also neighbouring plants are affected, becoming more attractive to predatory mites and less susceptible to spider mites. The mechanism involved in such interactions, however, remains elusive. Here we show that uninfested lima bean leaves activate five separate defence genes when exposed to volatiles from conspecific leaves infested with T. urticae, but not when exposed to volatiles from artificially wounded leaves. The expression pattern of these genes is similar to that produced by exposure to jasmonic acid. At least three terpenoids in the volatiles are responsible for this gene activation; they are released in response to herbivory but not artificial wounding. Expression of these genes requires calcium influx and protein phosphorylation/dephosphorylation.

Interactions of hydroxyapatite and fluorapatite particles on human osteoarthritis type B synoviocytes: effects on interleukin-1 alpha levels and lipoxygenase pathways

We investigated the effects of the biomaterials hydroxyapatite (HAP) and fluorapatite (FAP) on cultured human osteoarthritis type B synoviocytes by analyzing interleukin-1 alpha (IL-1 alpha) production and arachidonic acid metabolism via lipoxygenase pathways. A portion of opsonized particles was endocytosed and was found in numerous phagolysosomes in human synoviocyte cytoplasms. The present study demonstrates that HAP and FAP calcined at 700 degrees C induced a decrease in IL-1 alpha production but markedly decreased the synthesis of lipoxygenase products after 1-month incubation with the particles. This model will allow us to study the possible inflammatory response (arachidonic acid metabolism, proinflammatory cytokines) that can be induced by any biomaterials used in orthopedics.

Metabolic profiling of oxylipins upon salicylate treatment in barley leaves--preferential induction of the reductase pathway by salicylate(1)

In barley leaves, 13-lipoxygenases (13-LOXs) are induced by salicylate (SA) and jasmonate. Here, we show by metabolic profiling that upon SA treatment, free linolenic acid and linoleic acid accumulate in a 10:1 ratio reflecting their relative occurrence in leaf tissues. Furthermore, 13-LOX-derived products are formed and specifically directed into the reductase branch of the LOX pathway leading mainly to the accumulation of (13S,9Z,11E,15Z)-13-hydroxy-9, 11,15-octadecatrienoic acid (13-HOT). Under these conditions, no accumulation of other products of the LOX pathway has been found. Moreover, exogenously applied 13-HOT led to PR1b expression suggesting for the time a role of hydroxy polyenoic fatty acid derivatives in plant defense reactions.

Oxidized low density lipoprotein suppresses expression of inducible cyclooxygenase in human macrophages

Atherogenesis involves several aspects of chronic inflammation and wound healing. Indeed, the atheroma is considered a special case of tissue response to injury. Injurious stimuli may include lipoproteins trapped within lesions where protein and lipid moieties have undergone chemical modifications. We have studied the effect of oxidized low density lipoproteins (ox-LDL) on inducible cyclooxygenase (Cox-2) in human monocyte-derived macrophages exposed to bacterial lipopolysaccharide (LPS). Levels of both Cox-2 and constitutive cyclooxygenase (Cox-1) were assessed using Western blot analysis. Prior incubation of macrophages with ox-LDL resulted in a strong inhibition of Cox-2 induced by LPS, without effect on Cox-1. The inhibitory effect was dependent on ox-LDL concentration and its onset was early in time (already detectable 1 hour after macrophage exposure to ox-LDL). Native LDL, and other forms of modified LDL, were without effect. The inhibition was dependent on endocytosis of ox-LDL and could be reproduced using the lipid extract from ox-LDL. Lysophosphatidylcholine, 7beta-hydroxycholesterol, and 7-oxocholesterol failed to mimic the inhibition, but oxidized arachidonic acid-containing phospholipids, produced by autoxidation of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, markedly inhibited Cox-2. The observation that ox-LDL downregulates Cox-2 in human macrophages may explain the fact that, within atheromata, the transformation of macrophages into foam cells results in attenuation of the inflammatory response, thus contributing to progression of atherogenesis.

Wound- and systemin-inducible calmodulin gene expression in tomato leaves

Using a calmodulin (CaM) cDNA as a probe in northern analyses, transgenic tomato plants that overexpress the prosystemin gene were found to express increased levels of CaM mRNA and protein in leaves compared to wild-type plants. These transgenic plants have been reported previously to express several wound-inducible defense-related genes in the absence of wounding. Calmodulin mRNA and protein levels were found to increase in leaves of young wild-type tomato plants after wounding, or treatment with systemin, methyl jasmonate, or linolenic acid. CaM mRNA appeared within 0.5 h after wounding or supplying young tomato plants with systemin, and peaked at 1 h. The timing of CaM gene expression is similar to the expression of the wound- or systemin-induced lipoxygenase and prosystemin genes, signal pathway genes whose expression have been reported to begin at 0.5-1 h after wounding and 1-2 h earlier than the genes coding for defensive proteinase inhibitor genes. The similarities in timing between the synthesis of CaM mRNA and the mRNAs for signal pathway components suggests that CaM gene expression may be associated with the signaling cascade that activates defensive genes in response to wounding.

Isolation of lipoxygenase cDNA clones from pea nodule mRNA

The pattern of lipoxygenase (LOX) gene expression was investigated in pea nodule tissues using the technique of in situ hybridization. Five lipoxygenase cDNAs were cloned from nodule mRNA by the RT-PCR and 3' RACE procedures. These clones (loxN1 to loxN5) show a high degree of sequence homology, except in the 3'-untranslated region. Gene-specific riboprobes were therefore generated from subclones carrying the 3'-untranslated regions in order to investigate tissue-specific gene expression. Northern blotting analysis revealed that loxN1 corresponded to a transcript that was expressed exclusively in roots and nodules but not in the aerial parts of the plant. However, none of the LOX genes appeared to be up-regulated in nodule tissue relative to uninfected roots. Starting with the incomplete cDNA clone for loxN1, the full coding sequence termed lox1:P.s:1 was obtained by further rounds of RT-PCR and 5' RACE procedures. In situ hybridization with nodule tissues revealed several different patterns of expression for the various LOX probes. However, none of the corresponding transcripts was expressed exclusively in the invasion zone, as might have been expected if one LOX gene product had been uniquely associated with the invasion process. In conclusion, this study provides no evidence for a direct role for any LOX gene product in plant-microbe interaction or host defence, but the fact that all the transcripts were expressed at the nodule apex suggests that LOX could be involved in the development of this organ.

Characterization of authentic recombinant pea-seed lipoxygenases with distinct properties and reaction mechanisms

The two major isoforms of lipoxygenase (LOX-2 and LOX-3) from pea (Pisum sativum L. cv. Birte) seeds have been cloned and expressed from full-length cDNAs as soluble, active, non-fusion proteins in Escherichia coli. A comparison of both isoforms purified to apparent homogeneity from E. coli and pea seeds has confirmed the authenticity of the recombinant products and established the properties of the native enzymes. Despite 86% similarity at the amino acid sequence level, the enzymes have distinct properties. They have been characterized in terms of specific activity, Fe content, optimum pH, substrate and product specificity, apparent Km and Vmax for the preferred substrate, linoleic acid, and interfacial behaviour with linoleic acid. We have used this evidence, in addition to EPR spectroscopy of the hydroperoxide-activated enzymes and estimates of kcat/Km, to propose different reaction mechanisms for linoleic acid oxidation for the two isoforms. The differences relate primarily to carbonyl production from linoleic acid for which we propose a mechanism. This implicates the release of a peroxyl radical in an aerobic hydroperoxidase reaction, as the source of the carbonyl compounds formed by dismutation of the liberated peroxyl radical.

Circadian expression of pineal 5-lipoxygenase mRNA

In lymphocytes, the pineal hormone, melatonin, suppresses 5-lipoxygenase (5-LO) gene expression. Because circadian fluctuations in melatonin content are prominent in the pineal, we hypothesized that 5-LO mRNA level in this gland is greater when melatonin is low (day) than at night. Using the reverse transcription/polymerase chain reaction we assayed the levels of mRNAs coding for 5-LO, serotonin N-acetyltransferase (NAT), and for a constitutive gene, cyclophilin, in rat pineals obtained at 10:30-11:00 h (day) or 24:30-01:00 (night). Cyclophilin mRNA was not affected by circadian rhythm, whereas 5-LO and NAT were affected in an opposite manner: 5-LO mRNA was high during the day, NAT mRNA at night. We propose that circadian pineal 5-LO expression might play a role in circadian regulation of pineal functioning.

A gene encoding a chloroplast-targeted lipoxygenase in tomato leaves is transiently induced by wounding, systemin, and methyl jasmonate

We investigated the relationship between the expression of lipoxygenase (LOX) genes and the systemin-dependent wound response in tomato (Lycopersicon esculentum) leaves. A polymerase chain reaction-based approach was used to isolate two tomato Lox cDNAs, called TomLoxC and TomLoxD. Both TomLOXC and TomLOXD amino acid sequences possess an N-terminal extension of about 60 residues that were shown by in vitro uptake to function as transit peptides, targeting these proteins into the chloroplast. Within 30 to 50 min following wounding or systemin or methyl jasmonate treatments, the TomLoxD mRNA level increased and reached a maximum between 1 and 2 h. TomLoxC mRNA was not detectable in leaves and was not found following wounding, but it was found in ripening fruits, indicating that the two tomato Lox genes are regulated in different tissues by different processes. The results suggest that the TomLoxD gene is up-regulated in leaves in response to wounding and encodes a chloroplast LOX that may play a role as a component of the octadecanoid defense-signaling pathway.

Ozone stress modulates amine oxidase and lipoxygenase expression in lentil (Lens culinaris) seedlings

The effect of ozone stress on polyamine metabolism and membrane lipid peroxidation in lentil seedlings through the amine oxidase and lipoxygenase activity and expression has been investigated. Ozone is shown to control the expression of these enzymes at the transcriptional level, down-regulating the amine oxidase gene and up-regulating the lipoxygenase gene. The decrease of amine oxidase activity correlated with the increase of putrescine concentration in the ozone-treated plantlets, whereas the increase of lipoxygenase activity was paralleled by enhanced membrane lipid peroxidation. Finally, polyamines are shown to inhibit lipoxygenase activity in lentils.

Molecular cloning of a ripening-specific lipoxygenase and its expression during wild-type and mutant tomato fruit development

A 94-kD protein that accumulates predominately in tomato (Ly-copersicon esculentum) fruit during ripening was purified, and antibodies specific for the purified protein were used to isolate cDNA clones from a red-ripe fruit cDNA library. A sequence analysis of these cDNAs and cross-reactivity of the 94-kD-specific antibodies to the soybean lipoxygenase (LOX) L-1, L-2, and L-3 proteins and soybean LOX L-1-specific antibodies to the 94-kD protein identified it as a member of the LOX gene family. Maximum levels of the 94-kD LOX mRNA and protein are present in breaker to ripe and red-ripe stages, respectively. Expression of 94-kD LOX in different tissues from mature green and red-ripe tomato fruits was found to be greatest in the radial walls of ripe fruit, but immunocytolocalization using tissue printing suggests that the highest accumulation of its protein occurs in locular jelly. None of 94-kD LOX is expressed in nonripening mutant fruits of any age. Never-ripe mutant fruit accumulate the 94-kD LOX mRNA to levels similar to those obtained in wild-type fruit, but fail to accumulate the 94-kD LOX protein. Collectively, the results show that expression of 94-kD LOX is regulated by the ripening process, and ethylene may play a role in its protein accumulation.

Identification of a methyl jasmonate-responsive region in the promoter of a lipoxygenase 1 gene expressed in barley grain

A genomic DNA fragment was isolated containing 5' upstream sequences and part of the open reading frame corresponding to the lipoxygenase 1 cDNA (LoxA) expressed in barley grains during development and germination. Lox1 transcription was shown to be methyl jasmonate (MeJA)- and wound-inducible in leaves, but Lox1 transcripts were not detected in mildew-infected leaves, although this is a commonly observed response to pathogenic attack in various plants. Transient gene expression assays were used to identify a promoter region involved in MeJA-responsive expression. Analysis of 5' and 3' promoter deletions indicated that sequences between -363 and -294 conferred MeJA-responsive expression. Deletions/replacements covering this part of the promoter further defined a MeJA-responsive region between -331 and -291. Insertion of the region -328 to -293 into the constitutive CaMV 35S promoter conferred MeJA-responsive expression. The 36 bp fragment contains the motif TGACG as inverted repeats, which has been previously identified as a binding site for bZIP transactivating factors. Site-directed mutagenesis on these TGACG motifs abolished MeJA-responsive expression, clearly identifying them as MeJA-responsive elements. Sequence comparisons found no similar motif in other characterized promoters of MeJA-inducible genes, but suggested a common spatial structure which may serve as a binding site for transacting factors involved in the MeJA signal transduction pathway.

Induction of HSP70 and polyubiquitin expression associated with plant virus replication

By examining the front of virus invasion in immature pea embryos infected with pea seed-borne mosaic virus (PSbMV), the selective control of different host genes has been observed. From our observations, the early responses to PSbMV replication can be grouped into three classes, inhibited host gene expression, induced host gene expression, and no effect on a normal host function. The expression of two heat-inducible genes encoding HSP70 and polyubiquitin was induced coordinately with the onset of virus replication and the down-regulation of two other genes encoding lipoxygenase and heat shock cognate protein. The down-regulation was part of a general suppression of host gene expression that may be achieved through the degradation of host transcripts. We discuss the possibilities of whether the induction of HSP70 and polyubiquitin genes represents a requirement for the respective protein products by the virus or is merely a consequence of the depletion of other host transcripts. The former is feasible, as the induction of both genes does result in increased HSP70 and ubiquitin accumulation. This also indicates that, in contrast to some animal virus infections, there is not a general inhibition of translation of host mRNAs following PSbMV infection. This selective control of host gene expression was observed in all cell types of the embryo and identifies mechanisms of cellular disruption that could act as triggers for symptom expression.

Lipoxygenase gene expression in the tobacco-Phytophthora parasitica nicotianae interaction

A recently isolated cDNA clone of tobacco (Nicotiana tabacum L.) lipoxygenase (LOX) was used to study LOX gene expression in tobacco cell-suspension cultures and intact plants in response to infection with Phytophthora parasitica nicotianae (Ppn). Southern blot analysis of tobacco DNA indicated that only a small number of LOX genes hybridize to this probe. These genes were not constitutively expressed to a detectable level in control cells and healthy plants. In contrast, a rapid and transient accumulation of transcripts occurred in cells and plants after treatment with elicitor and inoculation with zoospores of Ppn, respectively. In cell cultures LOX gene expression could also be induced by linolenic acid, a LOX substrate, and by methyl jasmonate, one of the products derived from the action of LOX on linolenic acid. In the infection assays, LOX gene expression and enzyme activity were observed earlier when the plants carried a resistance gene against the race of Ppn used for inoculation. The differential expression of LOX during the race-cultivar-specific interaction between tobacco and Ppn, as well as its regulation by elicitors and jasmonate, suggest a role of LOX in plant resistance and establishment of the defense status against this pathogen.

Lipid body lipoxygenase characterized by protein fragmentation, cDNA sequence and very early expression of the enzyme during germination of cucumber seeds

Lipid bodies are cellular compartments containing triacylglycerols. They are encompassed by a phospholipid monolayer and decorated with characteristic proteins. In plants, lipid bodies are synthesized during seed formation but acquire new proteins during seed germination. In germinating cucumber (Cucumis sativus) seeds, the set of newly synthesized proteins appearing in the lipid bodies at the early stage of triacylglycerol mobilization comprises a special form of lipoxygenase. We isolated the lipid body lipoxygenase and characterized fragments prepared by limited proteolysis and cleavage with cyanogen bromide. A very early expression of lipid body lipoxygenase was found by studying the rate of de novo synthesis of lipoxygenase forms during germination. This allowed a clear distinction of this enzyme from other lipoxygenase isoforms. Hence, for determining the molecular structure of lipid body lipoxygenase we analyzed a cDNA prepared from mRNA of cotyledons at day 1 of germination. From the cDNA sequence, oligonucleotides were derived that specifically detected lipid body lipoxygenase mRNA on northern blots. The very early expression of lipid body lipoxygenase was corroborated by this approach. Good agreement was observed between the amino acid sequence deduced from the cDNA sequence and the peptide structures analyzed biochemically. In particular, the cleavage products of cyanogen bromide treatment indicated that we had isolated the lipid body lipoxygenase cDNA. The sequence data show a lipoxygenase form characterized by a molecular mass of 99655 Da, which is significantly higher than the molecular masses of the cytosolic forms. Compared to the cytosolic forms that exhibit a molecular mass of 95 kDa, the lipid body form has an N-terminal extension of 34 amino acid residues. No evidence for a cotranslational or post-translational proteolytic processing was obtained by the size comparison of the in vitro-translated lipoxygenase and the lipid body form.