Biotransformation of polyunsaturated fatty acids to bioactive hepoxilins and trioxilins by microbial enzymes

Critical Involvement of the Thioredoxin Reductase Gene (trxB) in Salmonella Gallinarum-Induced Systemic Infection in Chickens

Salmonella enterica serovar Gallinarum biovar Gallinarum (SG) causes fowl typhoid, a notifiable infectious disease in poultry. However, the pathogenic mechanism of SG-induced systemic infection in chickens remains unclear. Thioredoxin reductase (TrxB) is a redox protein crucial for regulating various enzyme activities in Salmonella serovar, but the role in SG-induced chicken systemic infection has yet to be determined. Here, we constructed a mutant SG strain lacking the trxB gene (trxB::Cm) and used chicken embryo inoculation and chicken oral infection to investigate the role of trxB gene in the pathogenicity of SG. Our results showed that trxB::Cm exhibited no apparent differences in colony morphology and growth conditions but exhibited reduced tolerance to H2O2 and increased resistance to bile acids. In the chicken embryo inoculation model, there was no significant difference in the pathogenicity of trxB::Cm and wild-type (WT) strains. In the chicken oral infection, the WT-infected group exhibited typical clinical symptoms of fowl typhoid, with complete mortality between days 6 and 9 post infection. In contrast, the trxB::Cm group showed a 100% survival rate, with no apparent clinical symptoms or pathological changes observed. The viable bacterial counts in the liver and spleen of the trxB::Cm-infected group were significantly reduced, accompanied by decreased expression of cytokines and chemokines (IL-1β, IL-6, IL-12, CXCLi1, TNF-α, and IFN-γ), which were significantly lower than those in the WT group. These results show that the pathogenicity of the trxB-deficient strain was significantly attenuated, indicating that the trxB gene is a crucial virulence factor in SG-induced systemic infection in chickens, suggesting that trxB may become a potentially effective target for controlling and preventing SG infection in chickens.

Biological Evaluations, NMR Analyses, Molecular Modeling Studies, and Overview of the Synthesis of the Marine Natural Product (-)-Mucosin

Natural products obtained from marine organisms continue to be a rich source of novel structural architecture and of importance in drug discovery, medicine, and health. However, the success of such endeavors depends on the exact structural elucidation and access to sufficient material, often by stereoselective total synthesis, of the isolated natural product of interest. (-)-Mucosin (1), a fatty acid derivative, previously presumed to contain a rare cis-bicyclo[4.3.0]non-3-ene moiety, has since been shown to be the trans-congener. Analytically, the fused bicyclic ring system in (-)-1 constitutes a particular challenge in order to establish its relative and absolute stereochemistry. Herein, data from biological evaluations, NMR and molecular modeling studies of (-)-1 are presented. An overview of the synthetic strategies enabling the exact structural elucidation of (-)-mucosin (1) is also presented.

Biotransformation of Polyunsaturated Fatty Acids to Trioxilins by Lipoxygenase from Pleurotus sajor-caju

A lipoxygenase from Pleurotus sajor-caju (PsLOX) was cloned, expressed in Escherichia coli, and purified as a soluble protein with a specific activity of 629 μmol/min/mg for arachidonic acid (AA). The native PsLOX exhibited a molecular mass of 146 kDa, including a 73-kDa homodimer, as estimated by gel-filtration chromatography. The major products converted from polyunsaturated fatty acids (PUFAs), including AA, eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), were identified as trioxilins (TrXs), namely 13,14,15-TrXB3 , 13,14,15-TrXB4 , and 15,16,17-TrXB5 , respectively, through high-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses. The enzyme displayed its maximum activity at pH 8.0 and 20 °C. Under these conditions, the specific activity and catalytic efficiency of PsLOX for PUFAs exhibited the following order: AA>EPA>DHA. Based on HPLC analysis and substrate specificity, PsLOX was identified as an arachidonate 15-LOX. PsLOX efficiently converted 10 mM of AA, EPA, and DHA to 8.7 mM of 13,14,15-TrXB3 (conversion rate: 87 %), 7.9 mM of 13,14,15-TrXB4 (79 %), and 7.2 mM of 15,16,17-TrXB5 (72 %) in 15, 20, and 20 min, respectively, marking the highest conversion rates reported to date. Collectively, our results demonstrate that PsLOX is an efficient TrXs-producing enzyme.

Sex-specific immune-inflammatory markers and lipoprotein profile in patients with anhedonia with unipolar and bipolar depression

BACKGROUND

Anhedonia is a core symptom in patients with unipolar and bipolar depression. However, sex-specific markers reflecting biological heterogeneity are lacking. Emerging evidence suggests that sex differences in immune-inflammatory markers and lipoprotein profiles are associated with anhedonia.

METHODS

The demographic and clinical data, immune-inflammatory markers (CD3, CD4, and CD8), and lipoprotein profiles [TC, TG, LDL-C, HDL-C, lipoprotein(a) Lp (a)] of 227 patients with unipolar and bipolar depression were collected. The Hamilton Depression Rating Scale (HAMD) and Snaith-Hamilton Pleasure Scale (SHAPS) were used to assess depression and anhedonia symptoms. Data were analyzed using ANOVA, logistic regression, and receiver operating characteristic curves.

RESULTS

Male patients in the anhedonia group had higher levels of CD3, CD4, and CD8, and lower levels of Lp (a) than the non-anhedonia group, while no significant difference was identified in female patients with and without anhedonia. Logistic regression analysis showed that CD3, CD4, CD8, and Lp (a) levels were associated with anhedonia in male patients. Furthermore, the combination of CD3, CD4, CD8, and Lp (a) had the strongest predictive value for distinguishing anhedonia in male patients than individual parameters.

CONCLUSIONS

We identified sex-specific associations between immune-inflammatory markers, lipoprotein profiles, and anhedonia in patients with unipolar and bipolar depression. The combination of CD3, CD4, CD8, and Lp (a) might be a possible biomarker for identifying anhedonia in male patients with unipolar and bipolar depression.

Extrinsic and intrinsic modulators of inflammation-resolution signaling in heart failure

Chronic and uncleared inflammation is the root cause of various cardiovascular diseases. Fundamentally, acute inflammation is supportive when overlapping with safe clearance of inflammation termed resolution; however, if the lifestyle-directed extrinsic factors such as diet, sleep, exercise, or physical activity are misaligned, that results in unresolved inflammation. Although genetics play a critical role in cardiovascular health, four extrinsic risk factors-unhealthy processed diet, sleep disruption or fragmentation, sedentary lifestyle, thereby, subsequent stress-have been identified as heterogeneous and polygenic triggers of heart failure (HF), which can result in several complications with indications of chronic inflammation. Extrinsic risk factors directly impact endogenous intrinsic factors, such as using fatty acids by immune-responsive enzymes [lipoxygenases (LOXs)/cyclooxygenases (COXs)/cytochromes-P450 (CYP450)] to form resolution mediators that activate specific resolution receptors. Thus, the balance of extrinsic factors such as diet, sleep, and physical activity feed-forward the coordination of intrinsic factors such as fatty acids-enzymes-bioactive lipid receptors that modulates the immune defense, metabolic health, inflammation-resolution signaling, and cardiac health. Future research on lifestyle- and aging-associated molecular patterns is warranted in the context of intrinsic and extrinsic factors, immune fitness, inflammation-resolution signaling, and cardiac health.

Engineering caveolin-mediated endocytosis in Saccharomyces cerevisiae

As a potential substitute for fatty acids, common low-cost oils could be used to produce acetyl-CoA derivatives, which meet the needs of low-cost industrial production. However, oils are hydrophobic macromolecules and cannot be directly transported into cells. In this study, caveolin was expressed in Saccharomyces cerevisiae to absorb exogenous oils. The expression of caveolin fused with green fluorescent protein showed that caveolin mediated the formation of microvesicles in S. cerevisiae and the addition of 5,6-carboxyfluorescein showed that caveolae had the ability to transport exogenous substances into cells. The intracellular and extracellular triacylglycerol levels were then detected after the addition of soybean oil pre-stained with Nile Red, which proved that caveolae had the ability to absorb the exogenous oils. Lastly, caveolin for oils absorption and lipase from Bacillus pumilus for oil hydrolysis were co-expressed in the naringenin-producing Saccharomyces cerevisiae strain, resulting in naringenin production increasing from 222 mg/g DCW (dry cell weight) (231 mg/L) to 269 mg/g DCW (241 mg/L). These results suggested that the caveolin-mediated transporter independent oil transport system would provide a promising strategy for the transport of hydrophobic substrates.

Deciphering and engineering the polyunsaturated fatty acid synthase pathway from eukaryotic microorganisms

Polyunsaturated fatty acids (PUFAs) are important nutrients that play important roles in human health. In eukaryotes, PUFAs can be de novo synthesized through two independent biosynthetic pathways: the desaturase/elongase pathway and the PUFA synthase pathway. Among them, PUFAs synthesized through the PUFA synthase pathway typically have few byproducts and require fewer reduction equivalents. In the past 2 decades, numerous studies have been carried out to identify, analyze and engineer PUFA synthases from eukaryotes. These studies showed both similarities and differences between the eukaryotic PUFA synthase pathways and those well studied in prokaryotes. For example, eukaryotic PUFA synthases contain the same domain types as those in prokaryotic PUFA synthases, but the number and arrangement of several domains are different; the basic functions of same-type domains are similar, but the properties and catalytic activities of these domains are somewhat different. To further utilize the PUFA synthase pathway in microbial cell factories and improve the productivity of PUFAs, many challenges still need to be addressed, such as incompletely elucidated PUFA synthesis mechanisms and the difficult genetic manipulation of eukaryotic hosts. In this review, we provide an updated introduction to the eukaryotic PUFA synthase pathway, summarize the functions of domains and propose the possible mechanisms of the PUFA synthesis process, and then provide future research directions to further elucidate and engineer the eukaryotic PUFA synthase pathway for the maximal benefits of humans.

Bioconversion of C20- and C22-polyunsaturated fatty acids into 9S,15S- and 11S,17S-dihydroxy fatty acids by Escherichia coli expressing double-oxygenating 9S-lipoxygenase from Sphingopyxis macrogoltabida

Double-oxygenating lipoxygenase (LOX) converted C20- and C22-polyunsaturated fatty acids (PUFAs) into C20 dihydroxy fatty acids (DiHFAs) as inflammatory mediators and C22 DiHFAs as specialized pro-resolving mediators, which are involved in the resolution of inflammation and infection in humans, and their isomers, respectively. However, the quantitative bioconversion of C20- and C22-PUFAs into 9S,15S- and 11S,17S-DiHFAs has been not attempted to date, respectively. Here, we performed the efficient quantitative production of 9S,15S- and 11S,17S-DiHFAs by Escherichia coli expressing 9S-LOX from Sphingopyxis macrogoltabida. The optimal bioconversion conditions of the C20 PUFA arachidonic acid or the C22-PUFA docosahexaenoic acid were pH 8.5, 35 °C, 6 mM substrate, and 5 g dry cells/L for C20 PUFAs or 7 g dry cells/L for C22 PUFAs, respectively. Under these conditions, E. coli expressing double-oxygenating 9S-LOX from S. macrogoltabida converted arachidonic acid, eicosapentaenoic acid, docosapentaenoic acid_n-3, and docosahexaenoic acid into 5.85 mM 9S,15S-dihydroxyeicosatetraenoic acid, 5.79 mM 9S,15S-dihydroxyeicosapentaenoic acid, 5.89 mM 11S,17S-hydroxydocosapentaenoic acid_n-3, and 5.24 mM 11S,17S-dihydroxydocosahexaenoic acid in 40, 30, 50, and 60 min, with conversion yields of 97.5%, 96.5%, 98.1%, and 87.3%; and volumetric productivities of 8.78, 11.6, 7.07, and 5.24 mM/h, respectively. To date, these are the highest concentrations, conversion yields, and volumetric productivities reported in the bioconversion of C20- and C22-PUFAs into DiHFAs.

Effects of Dietary n-3 and n-6 Polyunsaturated Fatty Acids in Inflammation and Cancerogenesis

The dietary recommendation encourages reducing saturated fatty acids (SFA) in diet and replacing them with polyunsaturated fatty acids (PUFAs) n-3 (omega-3) and n-6 (omega-6) to decrease the risk of metabolic disturbances. Consequently, excessive n-6 PUFAs content and high n-6/n-3 ratio are found in Western-type diet. The importance of a dietary n-6/n-3 ratio to prevent chronic diseases is linked with anti-inflammatory functions of linolenic acid (ALA, 18:3n-3) and longer-chain n-3 PUFAs. Thus, this review provides an overview of the role of oxylipins derived from n-3 PUFAs and oxylipins formed from n-6 PUFAs on inflammation. Evidence of PUFAs' role in carcinogenesis was also discussed. In vitro studies, animal cancer models and epidemiological studies demonstrate that these two PUFA groups have different effects on the cell growth, proliferation and progression of neoplastic lesions.

Molecular insights into lipoxygenases for biocatalytic synthesis of diverse lipid mediators

Oxylipins derived mainly from C20- and C22-polyunsaturated fatty acids (PUFAs), termed lipid mediators (LMs), are essential signalling messengers involved in human physiological responses associated with homeostasis and healing process for infection and inflammation. Some LMs involved in the resolution of inflammation and infection are termed specialized pro-resolving mediators (SPMs), which are generated by human M2 macrophages or polymorphonuclear leukocytes and have the potential to protect and treat hosts from bacterial and viral infections by phagocytosis activation. Lipoxygenases (LOXs) biosynthesize regio- and stereoselective LMs. Thus, understanding the regio- and stereoselectivities of LOXs for PUFAs at a molecular level is important for the biocatalytic synthesis of diverse LMs. Here, we elucidate the catalytic mechanisms and discuss regio- and stereoselectivities and their changes of LOXs determined by insertion direction and position of the substrate and oxygen at a molecular level for the biosynthesis of diverse human LMs. Recently, the biocatalytic synthesis of PUFAs to human LMs or analogues has been conducted using microbial LOXs. Such microbial LOXs involved in the biosynthesis of LMs are expected to exert significantly higher activity and stability than human LOXs. Diverse regio- and stereoselective LOXs can be obtained from microorganisms, which represent a wealth of genomic sources. We reconstruct the biosynthetic pathways of LOX-catalyzed LMs in humans and other organisms. Furthermore, we suggest the effective methods of biocatalytic synthesis of diverse human LMs from PUFAs or glucose by using microbial LOXs, increasing the stability and activity of LOXs, combining the reactions of LOXs, and constructing metabolic pathways.

An integrative approach to improving the biocatalytic reactions of whole cells expressing recombinant enzymes

Biotransformation is a selective, stereospecific, efficient, and environment friendly method, compared to chemical synthesis, and a feasible tool for industrial and pharmaceutical applications. The design of biocatalysts using enzyme engineering and metabolic engineering tools has been widely reviewed. However, less importance has been given to the biocatalytic reaction of whole cells expressing recombinant enzymes. Along with the remarkable development of biotechnology tools, a variety of techniques have been applied to improve the biocatalytic reaction of whole cell biotransformation. In this review, techniques related to the biocatalytic reaction are examined, reorganized, and summarized via an integrative approach. Moreover, equilibrium-shifted biotransformation is reviewed for the first time.

Biocatalytic synthesis of dihydroxy fatty acids as lipid mediators from polyunsaturated fatty acids by double dioxygenation of the microbial 12S-lipoxygenase

Leukotrienes (LTs) and maresins (MaRs) are human lipid mediators (LMs) involved in immune response and anti-inflammation, respectively. These compounds and their isomers are generated in trace amounts by lipoxygenases (LOXs) in human macrophages and neutrophils. These LMs have been synthesized using nonenvironmentally benign synthetic protocols, which are expensive. 8S- and 15S-LOXs with double dioxygenating activities have previously been reported, whereas 12S-LOX with double dioxygenating activity have not been reported to date. Here, we discovered a wild-type 12S-LOX with double dioxygenating activity from the bacterium Endozoicomonas numazuensis, which produced dihydroxy fatty acids (DiHFAs) as LMs from polyunsaturated fatty acids via double dioxygenation. The enzyme activity for producing DiHFA was approximately 550-fold higher than that of mammalian LOX with double dioxygenating activity. The microbial 12S-LOX converted 3.00 mM of arachidonic acid, eicosapentaenoic acid, docosapentaenoic acid, and docosahexaenoic acid to 2.37 mM (797 mg/L) 6-trans-8-cis-12S-epimer of LTB4, 1.59 mM (532 mg/L) 6-trans-8-cis-12S-epimer of LTB5, 1.35 mM (498 mg/L) 10-cis-12-trans-7S-epimer of MaR1_{n-3 DPA} , and 1.54 mM (555 mg/L) 10-cis-12-trans-7S-epimer of MaR1 within 2 h, which were 5.3-, 7.6-, 3.1-, and 5.5-fold higher than those biosynthesized by the previously reported microbial engineered 12S-LOX with double dioxygenating activity, respectively. These findings contribute to the efficient and environmentally friendly biosynthesis of LMs and stimulate physiological study on LMs.

Synthesis of two new lipid mediators from docosahexaenoic acid by combinatorial catalysis involving enzymatic and chemical reaction

Omega-3 polyunsaturated fatty acids (PUFAs) have been known to have beneficial effects in the prevention of various diseases. Recently, it was identified that the bioactivities of omega-3 are related to lipid mediators, called pro-resolving lipid mediators (SPMs), converted from PUFAs, so they have attracted much attention as potential pharmaceutical targets. Here, we aimed to build an efficient production system composed of enzymatic and chemical catalysis that converts docosahexaenoic acid (DHA) into lipid mediators. The cyanobacterial lipoxygenase, named Osc-LOX, was identified and characterized, and the binding poses of enzyme and substrates were predicted by ligand docking simulation. DHA was converted into three lipid mediators, a 17S-hydroxy-DHA, a 7S,17S-dihydroxy-DHA (RvD5), and a 7S,15R-dihydroxy-16S,17S-epoxy-DPA (new type), by an enzymatic reaction and deoxygenation. Also, two lipid mediators, 7S,15R,16S,17S-tetrahydroxy-DPA (new type) and 7S,16R,17S-trihydroxy-DHA (RvD2), were generated from 7S,15R-dihydroxy-16S,17S-epoxy-DPA by a chemical reaction. Our study suggests that discovering new enzymes that have not been functionally characterized would be a powerful strategy for producing various lipid mediators. Also, this combination catalysis approach including biological and chemical reactions could be an effective production system for the manufacturing lipid mediators.

Secretion of Pseudomonas aeruginosa Lipoxygenase by Pichia pastoris upon Glycerol Feed

Pseudomonas aeruginosa lipoxygenase (PaLOX) catalyzes the peroxidation of unsaturated fatty acids. Not only linoleic acid, but also linolenic acid and oleic acid are oxidized. The natural host secretes PaLOX into the periplasmic space. Herein, the aim is to secrete PaLOX to the culture supernatant of Pichia pastoris. Since protein background in the culture supernatant is typically rather low, this strategy allows for almost pure production of PaLOX applicable for the valorization of renewable fatty acids, for example for the production of green leaf volatiles. Using the CAT1 promoter system and the well-established α-factor signal sequence for secretion, methanol- and glycerol-induced secretion are compared and the latter shows four times more LOX activity in the culture supernatant under methanol-free conditions. In addition, secreted PaLOX is purified and the specific activity with enzyme in culture supernatant is compared. Notably, the predominant specific activity is achieved for enzyme in culture supernatant - 11.6 U mg^-1 - reaching five times higher specific activity than purified PaLOX.

Resolvin D5, a Lipid Mediator, Inhibits Production of Interleukin-6 and CCL5 Via the ERK-NF-κB Signaling Pathway in Lipopolysaccharide-Stimulated THP-1 Cells

One of the omega-3 essential fatty acids, docosahexaenoic acid (DHA), is a significant constituent of the cell membrane and the precursor of several potent lipid mediators. These mediators are considered to be important in preventing or treating several diseases. Resolvin D5, an oxidized lipid mediator derived from DHA, has been known to exert anti-inflammatory effects. However, the detailed mechanism underlying these effects has not yet been elucidated in human monocytic THP-1 cells. In the present study, we investigated the effects of resolvin D5 on inflammation-related signaling pathways, including the extracellular signal-regulated kinase (ERK)-nuclear factor (NF)-κB signaling pathway. Resolvin D5 downregulated the production of interleukin (IL)-6 and chemokine (C-C motif) ligand 5 (CCL5). Additionally, these inhibitory effects were found to be modulated by mitogen-activated protein kinase (MAPK) and NF-κB in lipopolysaccharide (LPS)-treated THP-1 cells. Resolvin D5 inhibited the LPS-stimulated phosphorylation of ERK and translocation of p65 and p50 into the nucleus, resulting in the inhibition of IL-6 and CCL5 production. These results revealed that resolvin D5 exerts anti-inflammatory effects in LPS-treated THP-1 cells by regulating the phosphorylation of ERK and nuclear translocation of NF-kappaB.

Design and engineering of whole-cell biocatalytic cascades for the valorization of fatty acids

This review presents the key factors to construct a productive whole-cell biocatalytic cascade exemplified for the biotransformation of renewable fatty acids.

Some Biogenetic Considerations Regarding the Marine Natural Product (-)-Mucosin

Recently, the identity of the marine hydrindane natural product (−)-mucosin was revised to the trans-fused structure 6, thereby providing a biogenetic puzzle that remains to be solved. We are now disseminating some of our insights with regard to the possible machinery delivering the established architecture. Aspects with regard to various modes of cyclization in terms of concerted versus stepwise processes are held up against the enzymatic apparatus known to be working on arachidonic acid (8). To provide a contrast to the tentative polyunsaturated fatty acid biogenesis, the structural pattern featured in (−)-mucosin (6) is compared to some marine hydrinane natural products of professed polyketide descent. Our appraisal points to a different origin and strengthens the hypothesis of a polyunsaturated fatty acids (PUFA) as the progenitor of (−)-mucosin (6).

Myxochelin- and Pseudochelin-Derived Lipoxygenase Inhibitors from a Genetically Engineered Myxococcus xanthus Strain

Precursor-directed biosynthesis was used to introduce selected aryl carboxylic acids into the pseudochelin pathway, which had recently been assembled in Myxococcus xanthus. Overall, 14 previously undescribed analogues of the natural products myxochelin B and pseudochelin A were generated and structurally characterized. A subset of 10 derivatives together with their parental molecules were evaluated for their activity toward human 5-lipoxygenase. This testing revealed pseudochelin A as the most potent 5-lipoxygenase inhibitor among the naturally occurring compounds, whereas myxochelin A is the least active. Replacement of the catechol moieties in myxochelin B and pseudochelin A affected the bioactivity to different degrees.

A new lipoxygenase from the agaric fungus Agrocybe aegerita: Biochemical characterization and kinetic properties

Oxylipins are metabolites with a variety of biological functions. However, the biosynthetic pathway is widely unknown. It is considered that the first step is the oxygenation of polyunsaturated fatty acids like linoleic acid. Therefore, a lipoxygenase (LOX) from the edible basidiomycete Agrocybe aegerita was investigated. The AaeLOX4 was heterologously expressed in E. coli and purified via affinity chromatography and gel filtration. Biochemical properties and kinetic parameters of the purified AaeLOX4 were determined with linoleic acid and linolenic acid as substrates. The obtained K_m, v_max and k_cat values for linoleic acid were 295.5 μM, 16.5 μM · min^-1 · mg^-1 and 103.9 s^-1, respectively. For linolenic acid K_m, v_max and k_cat values of 634.2 μM, 19.5 μM · min^-1 · mg^-1 and 18.3 s^-1 were calculated. Maximum activities were observed at pH 7.5 and 25 °C. The main product of linoleic acid conversion was identified with normal-phase HPLC. This analysis revealed an explicit production of 13-hydroperoxy-9,11-octadecadienoic acid (13-HPOD). The experimental regio specificity is underpinned by the amino acid residues W384, F450, R594 and V635 considered relevant for regio specificity in LOX. In conclusion, HPLC-analysis and alignments revealed that AaeLOX4 is a 13-LOX.

Endocytosing Escherichia coli as a Whole-Cell Biocatalyst of Fatty Acids

Whole cell biocatalysts can be used to convert fatty acids into various value-added products. However, fatty acid transport across cellular membranes into the cytosol of microbial cells limits substrate availability and impairs membrane integrity, which in turn decreases cell viability and bioconversion activity. Because these problems are associated with the mechanism of fatty acid transport through membranes, a whole-cell biocatalyst that can form caveolae-like structures was generated to promote substrate endocytosis. Caveolin-1 ( CAV1) expression in Escherichia coli increased both the fatty acid transport rate and intracellular fatty acid concentrations via endocytosis of the supplemented substrate. Furthermore, fatty-acid endocytosis alleviated substrate cytotoxicity in E. coli. These traits attributed to bacterial endocytosis resulted in dramatically elevated biotransformation efficiencies in fed-batch and cell-recycle reaction systems when caveolae-forming E. coli was used for the bioconversion of ricinoleic acid (12-hydroxyoctadec-9-enoic acid) to ( Z)-11-(heptanoyloxy) undec-9-enoic acid. We propose that CAV1-mediated endocytosing E. coli represents a versatile tool for the biotransformation of hydrophobic substrates.

Microbial Synthesis of Linoleate 9 S-Lipoxygenase Derived Plant C18 Oxylipins from C18 Polyunsaturated Fatty Acids

Plant oxylipins, including hydroxy fatty acids, epoxy hydroxy fatty acids, and trihydroxy fatty acids, which are biosynthesized from C18 polyunsaturated fatty acids (PUFAs), are involved in pathogen-specific defense mechanisms against fungal infections. However, their quantitative biotransformation by plant enzymes has not been reported. A few bacteria produce C18 trihydroxy fatty acids, but the enzymes and pathways related to the biosynthesis of plant oxylipins in bacteria have not been reported. In this study, we first report the biotransformation of C18 PUFAs into plant C18 oxylipins by expressing linoleate 9 S-lipoxygenase with and without epoxide hydrolase from the proteobacterium Myxococcus xanthus in recombinant Escherichia coli. Among the nine types of plant oxylipins, 12,13-epoxy-14-hydroxy- cis, cis-9,15-octadecadienoic acid was identified as a new compound by NMR analysis, and 9,10,11-hydroxy- cis, cis-6,12-octadecadienoic acid and 12,13,14-trihydroxy- cis, cis-9,15-octadecadienoic were suggested as new compounds by LC-MS/MS analysis. This study shows that bioactive plant oxylipins can be produced by microbial enzymes.

Stabilization and improved activity of arachidonate 11S-lipoxygenase from proteobacterium Myxococcus xanthus

Lipoxygenases (LOXs) catalyze the dioxygenation of PUFAs to produce regio- and stereospecific oxygenated fatty acids. The identification of regio- and stereospecific LOXs is important because their specific products are involved in different physiological activities in various organisms. Bacterial LOXs are found only in some proteobacteria and cyanobacteria, and they are not stable in vitro. Here, we used C20 and C22 PUFAs such as arachidonic acid (ARA), eicosapentaenoic acid, and docosahexaenoic acid to identify an 11S-specific LOX from the proteobacterium Myxococcus xanthus and explore its in vitro stability and activity. The activity and stability of M. xanthus ARA 11S-LOX as well as the production of 11S-hydroxyeicosatetraenoic acid from ARA were significantly increased by the addition of phosphatidylcholine, Ca²⁺, and coactosin-like protein (newly identified in the yeast Rhodosporidium toluroides) as stimulatory factors; in fact, LOX activity in the presence of all three factors increased approximately 3-fold. Our results indicate that these stimulatory factors can be used to increase the activity and stability of bacterial LOX and the production of bioactive hydroxy fatty acids, which can contribute to new academic research.