The Chemical Reactivity of Membrane Lipids

It is well-known that aqueous dispersions of phospholipids spontaneously assemble into bilayer structures. These structures have numerous applications across chemistry and materials science and form the fundamental structural unit of the biological membrane. The particular environment of the lipid bilayer, with a water-poor low dielectric core surrounded by a more polar and better hydrated interfacial region, gives the membrane particular biophysical and physicochemical properties and presents a unique environment for chemical reactions to occur. Many different types of molecule spanning a range of sizes, from dissolved gases through small organics to proteins, are able to interact with membranes and promote chemical changes to lipids that subsequently affect the physicochemical properties of the bilayer. This Review describes the chemical reactivity exhibited by lipids in their membrane form, with an emphasis on conditions where the lipids are well hydrated in the form of bilayers. Key topics include the following: lytic reactions of glyceryl esters, including hydrolysis, aminolysis, and transesterification; oxidation reactions of alkenes in unsaturated fatty acids and sterols, including autoxidation and oxidation by singlet oxygen; reactivity of headgroups, particularly with reactive carbonyl species; and E/Z isomerization of alkenes. The consequences of reactivity for biological activity and biophysical properties are also discussed.

A novel soluble di-iron monooxygenase from the soil bacterium Solimonas soli

Soluble di-iron monooxygenase (SDIMO) enzymes enable insertion of oxygen into diverse substrates and play significant roles in biogeochemistry, bioremediation and biocatalysis. An unusual SDIMO was detected in an earlier study in the genome of the soil organism Solimonas soli, but was not characterized. Here, we show that the S. soli SDIMO is part of a new clade, which we define as 'Group 7'; these share a conserved gene organization with alkene monooxygenases but have only low amino acid identity. The S. soli genes (named zmoABCD) could be functionally expressed in Pseudomonas putida KT2440 but not in Escherichia coli TOP10. The recombinants made epoxides from C2 C8 alkenes, preferring small linear alkenes (e.g. propene), but also epoxidating branched, carboxylated and chlorinated substrates. Enzymatic epoxidation of acrylic acid was observed for the first time. ZmoABCD oxidised the organochlorine pollutants vinyl chloride (VC) and cis-1,2-dichloroethene (cDCE), with the release of inorganic chloride from VC but not cDCE. The original host bacterium S. soli could not grow on any alkenes tested but grew well on phenol and n-octane. Further work is needed to link ZmoABCD and the other Group 7 SDIMOs to specific physiological and ecological roles.

Functional production and biochemical investigation of an integral membrane enzyme for olefin biosynthesis

Integral membrane enzymes play essential roles in a plethora of biochemical processes. The fatty acid desaturases (FADS)-like superfamily is an important group of integral membrane enzymes that catalyze a wide array of reactions, including hydroxylation, desaturation, and cyclization; however, due to the membrane-bound nature, the majority of these enzymes have remained poorly understood. UndB is a member of the FADS-like superfamily, which catalyzes fatty acid decarboxylation, a chemically challenging reaction at the membrane interface. UndB reaction produces terminal olefins that are prominent biofuel candidates and building blocks of polymers with widespread industrial applications. Despite the great importance of UndB for several biotechnological applications, the enzyme has eluded comprehensive investigation. Here, we report details of the expression, solubilization, and purification of several constructs of UndB to achieve the optimally functional enzyme. We gained important insights into the biochemical, biophysical, and catalytic properties of UndB, including the thermal stability and factors influencing the enzyme activity. Additionally, we established the ability and kinetics of UndB to produce dienes by performing di-decarboxylation of diacids. We found that the reaction proceeds by forming a mono-carboxylic acid intermediate. Our findings shed light on the unexplored biochemical properties of the UndB and extend opportunities for its rigorous mechanistic and structural characterization.

The 2-methylpropene degradation pathway in Mycobacteriaceae family strains

Mycolicibacterium gadium IBE100 and Mycobacterium paragordonae IBE200 are aerobic, chemoorganoheterotrophic bacteria isolated from activated sludge from a wastewater treatment plant. They use 2-methylpropene (isobutene, 2-MP) as the sole source of carbon and energy. Here, we postulate a degradation pathway of 2-methylpropene derived from whole genome sequencing, differential expression analysis and peptide-mass fingerprinting. Key genes identified are coding for a 4-component soluble diiron monooxygenase with epoxidase activity, an epoxide hydrolase, and a 2-hydroxyisobutyryl-CoA mutase. In both strains, involved genes are arranged in clusters of 61.0 and 58.5 kbp, respectively, which also contain the genes coding for parts of the aerobic pathway of adenosylcobalamin synthesis. This vitamin is essential for the carbon rearrangement reaction catalysed by the mutase. These findings provide data for the identification of potential 2-methylpropene degraders.

P450 fatty acid decarboxylase

P450 fatty acid decarboxylases are able to utilize hydrogen peroxide as the sole cofactor to decarboxylate free fatty acids to produce α-olefins with abundant applications as drop-in biofuels and important chemical precursors. In this chapter, we review diverse approaches for discovery, characterization, engineering, and applications of P450 fatty acid decarboxylases. Information gained from structural data has been advancing our understandings of the unique mechanisms underlying alkene production, and providing important insights for exploring new activities. To build an efficient olefin-producing system, various engineering strategies have been proposed and applied to this unusual P450 catalytic system. Furthermore, we highlight a select number of applied examples of P450 fatty acid decarboxylases in enzyme cascades and metabolic engineering.

Engineering cytochrome P450s for selective alkene to carbonyl oxidation

The Wacker-Tsuji oxidation is an important aerobic oxidation process to synthesize ethanal from ethene and methyl ketones from 1-alkenes. Current challenges in aerobic alkene oxidation include selective carbonyl product formation beyond methyl ketones. This includes the regioselective oxidation of the terminal carbon atom of 1-alkenes, the regioselective ketone formation with internal alkenes as well as the enantioselective alkene to carbonyl oxidation. Recently, the potential of high-valent metal-oxo species for direct alkene to carbonyl oxidation was explored as carbonyl product formation is frequently reported as a side reaction of alkene epoxidation by cytochrome P450s. It was shown that such promiscuous P450s can be engineered via directed evolution to perform alkene to carbonyl oxidation reactions with high activity and selectivity. Here, we report a protocol to convert promiscuous P450s into efficient and selective enzymes for Wacker-type alkene oxidation. One round of directed evolution is described in detail, which includes the generation and handling of site-saturation libraries, recombinant protein expression, library screening in a 96-well plate format and the rescreening of variants with beneficial mutations. These protocols might be useful to engineer various P450s for selective alkene to carbonyl oxidation, and to engineer enzymes in general.

Overexpression of SmLAC25 promotes lignin accumulation and decreases salvianolic acid content in Salvia miltiorrhiza

Laccase (LAC) is a blue multicopper oxidase that contains four copper ions, which is involved in lignin polymerization and flavonoid biosynthesis in plants. Although dozens of LAC genes have been identified in Salvia miltiorrhiza Bunge (a model medicinal plant), most have not been functionally characterized. Here, we explored the expression patterns and the functionality of SmLAC25 in S. miltiorrhiza. SmLAC25 has a higher expression level in roots and responds to methyl jasmonate, auxin, abscisic acid, and gibberellin stimuli. The SmLAC25 protein is localized in the cytoplasm and chloroplasts. Recombinant SmLAC25 protein could oxidize coniferyl alcohol and sinapyl alcohol, two monomers of G-lignin and S-lignin. To investigate its function, we generated SmLAC25-overexpressed S. miltiorrhiza plantlets and hairy roots. The lignin content increased significantly in all SmLAC25-overexpressed plantlets and hairy roots, compared with the controls. However, the concentrations of rosmarinic acid and salvianolic acid B decreased significantly in all the SmLAC25-overexpressed lines. Further studies revealed that the transcription levels of some key enzyme genes in the lignin synthesis pathway (e.g., SmCCR and SmCOMT) were significantly improved in the SmLAC25-overexpressed lines, while the expression levels of multiple enzyme genes in the salvianolic acid biosynthesis pathway were inhibited. We speculated that the overexpression of SmLAC25 promoted the metabolic flux of lignin synthesis, which resulted in a decreased metabolic flux to the salvianolic acid biosynthesis pathway.

Insights into cyanobacterial alkane biosynthesis

Alkanes are high-energy molecules that are compatible with enduring liquid fuel infrastructures, which make them highly suitable for being next-generation biofuels. Though biological production of alkanes has been reported in various microorganisms, the reports citing photosynthetic cyanobacteria as natural producers have been the most consistent for the long-chain alkanes and alkenes (C15-C19). However, the production of alkane in cyanobacteria is low, leading to its extraction being uneconomical for commercial purposes. In order to make alkane production economically feasible from cyanobacteria, the titre and yield need to be increased by several orders of magnitude. In the recent past, efforts have been made to enhance alkane production, although with a little gain in yield, leaving space for much improvement. Genetic manipulation in cyanobacteria is considered challenging, but recent advancements in genetic engineering tools may assist in manipulating the genome in order to enhance alkane production. Further, advancement in a basic understanding of metabolic pathways and gene functioning will guide future research for harvesting the potential of these tiny photosynthetically efficient factories. In this review, our focus would be to highlight the current knowledge available on cyanobacterial alkane production, and the potential aspects of developing cyanobacterium as an economical source of biofuel. Further insights into different metabolic pathways and hosts explored so far, and possible challenges in scaling up the production of alkanes will also be discussed.

Herbivore-induced volatiles influence moth preference by increasing the β-Ocimene emission of neighbouring tea plants

Herbivore-induced plant volatiles prime neighbouring plants to respond more strongly to subsequent attacks. However, the key volatiles that trigger this state and their priming mechanisms remain largely unknown. The tea geometrid Ectropis obliqua is one of the most devastating leaf-feeding pests of tea plants. Here, plant-plant communication experiments demonstrated that volatiles emitted from tea plants infested by E. obliqua larvae triggered neighbouring plants to release volatiles that repel E. obliqua adult, especially mated females. Volatile analyses revealed that the quantity of eight volatiles increased dramatically when plants were exposed to volatiles emitted by infested tea plants, including (Z)-3-hexenol, linalool, α-farnesene, β-Ocimene and (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT). The results of behavioural bioassays demonstrated that β-Ocimene strongly repelled mated E. obliqua females. Individual volatile compound exposure experiments revealed that (Z)-3-hexenol, linalool, α-farnesene and DMNT triggered the emission of β-Ocimene from tea plants. Chemical inhibition experiments demonstrated that the emission of β-Ocimene induced by (Z)-3-hexenol, linalool, α-farnesene and DMNT were dependent on Ca²⁺ and JA signalling. These findings help us to understand how E. obliqua moths respond to volatiles emitted from tea plants and provide new insight into volatile-mediated plant-plant interactions. They have potential significance for the development of novel insect and pest control strategies in crops.

Prevalence of toxigenic fungi and mycotoxins in Arabic coffee (Coffea arabica): Protective role of traditional coffee roasting, brewing and bacterial volatiles

Fungal infection and synthesis of mycotoxins in coffee leads to significant economic losses. This study aimed to investigate the prevalence of toxigenic fungi, their metabolites, and the effect of traditional roasting and brewing on ochratoxin A (OTA) and aflatoxins (AFs) contents of naturally contaminated coffee samples. In addition, in vivo biocontrol assays were performed to explore the antagonistic activities of Bacillus simplex 350–3 (BS350-3) on the growth and mycotoxins synthesis of Aspergillus ochraceus and A. flavus. The relative density of A. niger, A. flavus, Penicillium verrucosum and A. carbonarius on green coffee bean was 60.82%, 7.21%, 3.09% and 1.03%, respectively. OTA contents were lowest in green coffee beans (2.15 μg/kg), followed by roasted (2.76 μg/kg) and soluble coffee (8.95 μg/kg). Likewise, AFs levels were highest in soluble coffee (90.58 μg/kg) followed by roasted (33.61 μg/kg) and green coffee (9.07 μg/kg). Roasting naturally contaminated coffee beans at three traditional methods; low, medium and high, followed by brewing resulted in reduction of 58.74% (3.50 μg/kg), 60.88% (3.72 μg/kg) and 64.70% (4.11 μg/kg) in OTA and 40.18% (34.65 μg/kg), 47.86% (41.17 μg/kg) and 62.38% (53.73 μg/kg) AFs contents, respectively. Significant inhibitions of AFs and OTA synthesis by A. flavus and A. carbonarius, respectively, on infected coffee beans were observed in presence of Bacillus simplex BS350-3 volatiles. Gas chromatography mass spectrochemistry (GC-MS/MS) analysis of head-space BS350-3 volatiles showed quinoline, benzenemethanamine and 1-Octadecene as bioactive antifungal molecules. These findings suggest that marketed coffee samples are generally contaminated with OTA and AFs, with a significant level of roasted and soluble coffee contaminated above EU permissible limits for OTA. Further, along with coffee roasting and brewing; microbial volatiles can be optimized to minimize the dietary exposure to mycotoxins.

Exploring Marine-Derived Ascochlorins as Novel Human Dihydroorotate Dehydrogenase Inhibitors for Treatment of Triple-Negative Breast Cancer

Human dihydroorotate dehydrogenase (hDHODH) is an attractive tumor target essential to de novo pyrimidine biosynthesis. Novel potent hDHODH inhibitors with low toxicity are urgently needed. Herein, we demonstrate the isolation of 25 ascochlorin (ASC) derivatives, including 13 new ones, from the coral-derived fungus Acremonium sclerotigenum, and several of them showed pronounced inhibitions against hDHODH and triple-negative breast cancer (TNBC) cell lines, MDA-MB-231/-468. Interestingly, we found that hDHODH is required for proliferation and survival of TNBC cells, and several ASCs significantly inhibited TNBC cell growth and induced their apoptosis via hDHODH inhibition. Furthermore, the novel and potent hDHODH inhibitors (1 and 21) efficiently suppressed tumor growth in patient-derived TNBC xenograft models without obvious body weight loss or overt toxicity in mice. Collectively, our findings offered a novel lead scaffold as the hDHODH inhibitor for further development of potent anticancer agents and a potential therapeutic strategy for TNBC.

Acyl-CoA desaturase ADS4.2 is involved in the formation of characteristic wax alkenes in young Arabidopsis leaves

Monounsaturated alkenes are present in the cuticular waxes of diverse plants and are thought to play important roles in their interactions with abiotic and biotic factors. Arabidopsis (Arabidopsis thaliana) leaf wax has been reported to contain alkenes; however, their biosynthesis has not been investigated to date. Here, we found that these alkenes have mainly ω-7 and ω-9 double bonds in characteristically long hydrocarbon chains ranging from C33 to C37. A screening of desaturase-deficient mutants showed that a single desaturase belonging to the acyl-CoA desaturase (ADS) family, previously reported as ADS4.2, was responsible for introducing double bonds en route to the wax alkenes. ADS4.2 was highly expressed in young leaves, especially in trichomes, where the alkenes are known to accumulate. The enzyme showed strong activity on acyl substrates longer than C32 and ω-7 product regio-specificity when expressed in yeast (Saccharomyces cerevisiae). Its endoplasmic reticulum localization further confirmed that ADS4.2 has access to very-long-chain fatty acyl-CoA substrates. The upstream biosynthesis pathways providing substrates to ADS4.2 and the downstream reactions forming the alkene products in Arabidopsis were further clarified by alkene analysis of mutants deficient in other wax biosynthesis genes. Overall, our results show that Arabidopsis produces wax alkenes through a unique elongation-desaturation pathway, which requires the participation of ADS4.2.

Genome-wide analysis of ARF transcription factors reveals HcARF5 expression profile associated with the biosynthesis of β-ocimene synthase in Hedychium coronarium

Herein, 37 ARF genes were identified and analyzed in Hedychium coronarium and HcARF5 showed a potential role in the regulation of HcTPS3. Auxin is an important plant hormone, implicated in various aspects of plant growth and development processes especially in the biosynthesis of various secondary metabolites. Auxin response factors (ARF) belong to the transcription factors (TFs) gene family and play a crucial role in transcriptional activation/repression of auxin-responsive genes by directly binding to their promoter region. Nevertheless, whether ARF genes are involved in the regulatory mechanism of volatile compounds in flowering plants is largely unknown. β-ocimene is a key floral volatile compound synthesized by terpene synthase 3 (HcTPS3) in Hedychium coronarium. A comprehensive analysis of H. coronarium genome reveals 37 candidate ARF genes in the whole genome. Tissue-specific expression patterns of HcARFs family members were assessed using available transcriptome data. Among them, HcARF5 showed a higher expression level in flowers, and significantly correlated with the key structural β-ocimene synthesis gene (HcTPS3). Furthermore, transcript levels of both genes were associated with the flower development. Under hormone treatments, the response of HcARF5 and HcTPS3, and the emission level of β-ocimene contents were evaluated. Subcellular and transcriptional activity assay showed that HcARF5 localizes to the nucleus and possesses transcriptional activity. Yeast one-hybrid (Y1H) and dual-luciferase assays revealed that HcARF5 directly regulates the transcriptional activity of HcTPS3. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays showed that HcARF5 interacts with scent-related HcIAA4, HcIAA6, and HcMYB1 in vivo. Overall, these results indicate that HcARF5 is potentially involved in the regulation of β-ocimene synthesis in H. coronarium.

Genome-wide analysis of ARF transcription factors reveals HcARF5 expression profile associated with the biosynthesis of β-ocimene synthase in Hedychium coronarium

Herein, 37 ARF genes were identified and analyzed in Hedychium coronarium and HcARF5 showed a potential role in the regulation of HcTPS3. Auxin is an important plant hormone, implicated in various aspects of plant growth and development processes especially in the biosynthesis of various secondary metabolites. Auxin response factors (ARF) belong to the transcription factors (TFs) gene family and play a crucial role in transcriptional activation/repression of auxin-responsive genes by directly binding to their promoter region. Nevertheless, whether ARF genes are involved in the regulatory mechanism of volatile compounds in flowering plants is largely unknown. β-ocimene is a key floral volatile compound synthesized by terpene synthase 3 (HcTPS3) in Hedychium coronarium. A comprehensive analysis of H. coronarium genome reveals 37 candidate ARF genes in the whole genome. Tissue-specific expression patterns of HcARFs family members were assessed using available transcriptome data. Among them, HcARF5 showed a higher expression level in flowers, and significantly correlated with the key structural β-ocimene synthesis gene (HcTPS3). Furthermore, transcript levels of both genes were associated with the flower development. Under hormone treatments, the response of HcARF5 and HcTPS3, and the emission level of β-ocimene contents were evaluated. Subcellular and transcriptional activity assay showed that HcARF5 localizes to the nucleus and possesses transcriptional activity. Yeast one-hybrid (Y1H) and dual-luciferase assays revealed that HcARF5 directly regulates the transcriptional activity of HcTPS3. Yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays showed that HcARF5 interacts with scent-related HcIAA4, HcIAA6, and HcMYB1 in vivo. Overall, these results indicate that HcARF5 is potentially involved in the regulation of β-ocimene synthesis in H. coronarium.

E. coli Nickel-Iron Hydrogenase 1 Catalyses Non-native Reduction of Flavins: Demonstration for Alkene Hydrogenation by Old Yellow Enzyme Ene-reductases*

A new activity for the [NiFe] uptake hydrogenase 1 of Escherichia coli (Hyd1) is presented. Direct reduction of biological flavin cofactors FMN and FAD is achieved using H2 as a simple, completely atom-economical reductant. The robust nature of Hyd1 is exploited for flavin reduction across a broad range of temperatures (25-70 °C) and extended reaction times. The utility of this system as a simple, easy to implement FMNH2 or FADH2 regenerating system is then demonstrated by supplying reduced flavin to Old Yellow Enzyme "ene-reductases" to support asymmetric alkene reductions with up to 100 % conversion. Hyd1 turnover frequencies up to 20.4 min-1 and total turnover numbers up to 20 200 were recorded during flavin recycling.

Chemical Variation among Castes, Female Life Stages and Populations of the Facultative Eusocial Sweat Bee Halictus rubicundus (Hymenoptera: Halictidae)

In eusocial insects, chemical communication is crucial for mediating many aspects of social activities, especially the regulation of reproduction. Though queen signals are known to decrease ovarian activation of workers in highly eusocial species, little is known about their evolution. In contrast, some primitively eusocial species are thought to control worker reproduction through physical aggression by the queen rather than via pheromones, suggesting the evolutionary establishment of chemical signals with more derived sociality. However, studies supporting this hypothesis are largely missing. Socially polymorphic halictid bees, such as Halictus rubicundus, with social and solitary populations in both Europe and North America, offer excellent opportunities to illuminate the evolution of caste-specific signals. Here we compared the chemical profiles of social and solitary populations from both continents and tested whether (i) population or social level affect chemical dissimilarity and whether (ii) caste-specific patterns reflect a conserved queen signal. Our results demonstrate unique odor profiles of European and North American populations, mainly due to different isomers of n-alkenes and macrocyclic lactones; chemical differences may be indicative of phylogeographic drift in odor profiles. We also found common compounds overproduced in queens compared to workers in both populations, indicating a potential conserved queen signal. However, North American populations have a lower caste-specific chemical dissimilarity than European populations which raises the question if both use different mechanisms of regulating reproductive division of labor. Therefore, our study gives new insights into the evolution of eusocial behavior and the role of chemical communication in the inhibition of reproduction.

Herbivore-induced DMNT catalyzed by CYP82D47 plays an important role in the induction of JA-dependent herbivore resistance of neighboring tea plants

Herbivore-induced plant volatiles play important ecological roles in defense against stresses. However, if and which volatile(s) are involved in the plant-plant communication in response to herbivorous insects in tea plants remains unknown. Here, plant-plant communication experiments confirm that volatiles emitted from insects-attacked tea plants can trigger plant resistance and reduce the risk of herbivore damage by inducing jasmonic acid (JA) accumulation in neighboring plants. The emission of six compounds was significantly induced by geometrid Ectropis obliqua, one of the most common pests of the tea plant in China. Among them, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) could induce the accumulation of JA and thus promotes the resistance of neighboring intact plants to herbivorous insects. CsCYP82D47 was identified for the first time as a P450 enzyme, which catalyzes the final step in the biosynthesis of DMNT from (E)-nerolidol. Down-regulation of CsCYP82D47 in tea plants resulted in a reduced accumulation of DMNT and significantly reduced the release of DMNT in response to the feeding of herbivorous insects. The first evidence for plant-plant communication in response to herbivores in tea plants will help to understand how plants respond to volatile cues in response to herbivores and provide new insight into the role(s) of DMNT in tea plants.

Cuticular and Dufour's Gland Chemistry Reflect Reproductive and Social State in the Facultatively Eusocial Sweat Bee Megalopta genalis (Hymenoptera: Halictidae)

Queen pheromones evolved independently in multiple eusocial insect lineages, in which they mediate reproductive conflict by inhibiting worker ovarian development. Although fundamentally important for reproductive division of labor - the hallmark of eusociality - their evolutionary origins are enigmatic. Here, we analyze cuticular and Dufour's gland chemistries across alternative social and reproductive phenotypes in Megalopta genalis bees (tribe Augochlorini, family Halictidae) that facultatively express simple eusociality. Reproductive bees have distinct overall glandular and cuticular chemical phenotypes compared with non-reproductive workers. On the cuticle, a likely site of signal transmission, reproductives are enriched for certain alkenes, most linear alkanes, and are heavily enriched for all methyl-branched alkanes. Chemicals belonging to these compound classes are known to function as fertility signals in other eusocial insect taxa. Some macrocyclic lactones, compounds that serve as queen pheromones in the other eusocial halictid tribe (Halictini), are also enriched among reproductives relative to workers. The intra-population facultative eusociality of M. genalis permits direct comparisons between individuals expressing alternative reproductive phenotypes - females that reproduce alone (solitary reproductives) and social queens - to highlight traits in the latter that may be important mediators of eusociality. Compared with solitary reproductives, the cuticular chemistries of queens are more strongly differentiated from those of workers, and furthermore are especially enriched for methyl-branched alkanes. Determining the pheromonal function(s) and information content of the candidate signaling compounds we identify will help illuminate the early evolutionary history of queen pheromones, chemical signals central to the organization of insect eusocial behavior.

Production of Propene from n-Butanol: A Three-Step Cascade Utilizing the Cytochrome P450 Fatty Acid Decarboxylase OleTJE

Propene is one of the most important starting materials in the chemical industry. Herein, we report an enzymatic cascade reaction for the biocatalytic production of propene starting from n-butanol, thus offering a biobased production from glucose. In order to create an efficient system, we faced the issue of an optimal cofactor supply for the fatty acid decarboxylase OleTJE , which is said to be driven by either NAD(P)H or H2 O2 . In the first system, we used an alcohol and aldehyde dehydrogenase coupled to OleTJE by the electron-transfer complex putidaredoxin reductase/putidaredoxin, allowing regeneration of the NAD+ cofactor. With the second system, we intended full oxidation of n-butanol to butyric acid, generating one equivalent of H2 O2 that can be used for the oxidative decarboxylation. As the optimal substrate is a long-chain fatty acid, we also tried to create an improved variant for the decarboxylation of butyric acid by using rational protein design. Within a mutational study with 57 designed mutants, we generated the mutant OleTV292I , which showed a 2.4-fold improvement in propene production in our H2 O2 -driven cascade system and reached total turnover numbers >1000.

Sub-lethal effects of the consumption of Eupatorium buniifolium essential oil in honeybees

When developing new products to be used in honeybee colonies, further than acute toxicity, it is imperative to perform an assessment of risks, including various sublethal effects. The long-term sublethal effects of xenobiotics on honeybees, more specifically of acaricides used in honeybee hives, have been scarcely studied, particularly so in the case of essential oils and their components. In this work, chronic effects of the ingestion of Eupatorium buniifolium (Asteraceae) essential oil were studied on nurse honeybees using laboratory assays. Survival, food consumption, and the effect on the composition of cuticular hydrocarbons (CHC) were assessed. CHC were chosen due to their key role as pheromones involved in honeybee social recognition. While food consumption and survival were not affected by the consumption of the essential oil, CHC amounts and profiles showed dose-dependent changes. All groups of CHC (linear and branched alkanes, alkenes and alkadienes) were altered when honeybees were fed with the highest essential oil dose tested (6000 ppm). The compounds that significantly varied include n-docosane, n-tricosane, n-tetracosane, n-triacontane, n-tritriacontane, 9-tricosene, 7-pentacosene, 9-pentacosene, 9-heptacosene, tritriacontene, pentacosadiene, hentriacontadiene, tritriacontadiene and all methyl alkanes. All of them but pentacosadiene were up-regulated. On the other hand, CHC profiles were similar in healthy and Nosema-infected honeybees when diets included the essential oil at 300 and 3000 ppm. Our results show that the ingestion of an essential oil can impact CHC and that the effect is dose-dependent. Changes in CHC could affect the signaling process mediated by these pheromonal compounds. To our knowledge this is the first report of changes in honeybee cuticular hydrocarbons as a result of essential oil ingestion.

SmMYB2 promotes salvianolic acid biosynthesis in the medicinal herb Salvia miltiorrhiza

MYB transcription factors play vital roles in plant growth and metabolism. The phytohormone methyl jasmonate (MeJA) promotes phenolic acid accumulation in the medicinal herb Salvia miltiorrhiza, but the regulatory mechanism is poorly understood. Here, we identified the MeJA-responsive R2R3-MYB transcription factor gene SmMYB2 from a transcriptome library produced from MeJA-treated S. miltiorrhiza hairy roots. SmMYB2 expression was tightly correlated with the expression of key salvianolic acid biosynthetic genes including CYP98A14. SmMYB2 was highly expressed in the periderm of S. miltiorrhiza and SmMYB2 localized to the nucleus. Overexpressing SmMYB2 in S. miltiorrhiza hairy roots significantly increased the levels of salvianolic acids (including rosmarinic acid and salvianolic acid B) by upregulating salvianolic acid biosynthetic genes such as CYP98A14. SmMYB2 binds to the MYB-binding motifs in the promoter of CYP98A14, as confirmed by a dual-luciferase assay and electrophoretic mobility shift assays. Anthocyanin contents were significantly higher in SmMYB2-overexpressing hairy root lines than the control, primarily due to the increased expression of CHI, DFR, and ANS. These findings reveal the novel regulatory role of SmMYB2 in MeJA-mediated phenolic acid biosynthesis, providing a useful target gene for metabolic engineering and shedding light on the salvianolic acid regulatory network.

SmMYB2 promotes salvianolic acid biosynthesis in the medicinal herb Salvia miltiorrhiza

MYB transcription factors play vital roles in plant growth and metabolism. The phytohormone methyl jasmonate (MeJA) promotes phenolic acid accumulation in the medicinal herb Salvia miltiorrhiza, but the regulatory mechanism is poorly understood. Here, we identified the MeJA-responsive R2R3-MYB transcription factor gene SmMYB2 from a transcriptome library produced from MeJA-treated S. miltiorrhiza hairy roots. SmMYB2 expression was tightly correlated with the expression of key salvianolic acid biosynthetic genes including CYP98A14. SmMYB2 was highly expressed in the periderm of S. miltiorrhiza and SmMYB2 localized to the nucleus. Overexpressing SmMYB2 in S. miltiorrhiza hairy roots significantly increased the levels of salvianolic acids (including rosmarinic acid and salvianolic acid B) by upregulating salvianolic acid biosynthetic genes such as CYP98A14. SmMYB2 binds to the MYB-binding motifs in the promoter of CYP98A14, as confirmed by a dual-luciferase assay and electrophoretic mobility shift assays. Anthocyanin contents were significantly higher in SmMYB2-overexpressing hairy root lines than the control, primarily due to the increased expression of CHI, DFR, and ANS. These findings reveal the novel regulatory role of SmMYB2 in MeJA-mediated phenolic acid biosynthesis, providing a useful target gene for metabolic engineering and shedding light on the salvianolic acid regulatory network.

Functional and morphological adaptation in DNA protocells via signal processing prompted by artificial metalloenzymes

For life to emerge, the confinement of catalytic reactions within protocellular environments has been proposed to be a decisive aspect to regulate chemical activity in space¹. Today, cells and organisms adapt to signals^2-6 by processing them through reaction networks that ultimately provide downstream functional responses and structural morphogenesis^7,8. Re-enacting such signal processing in de novo-designed protocells is a profound challenge, but of high importance for understanding the design of adaptive systems with life-like traits. We report on engineered all-DNA protocells⁹ harbouring an artificial metalloenzyme¹⁰ whose olefin metathesis activity leads to downstream morphogenetic protocellular responses with varying levels of complexity. The artificial metalloenzyme catalyses the uncaging of a pro-fluorescent signal molecule that generates a self-reporting fluorescent metabolite designed to weaken DNA duplex interactions. This leads to pronounced growth, intraparticular functional adaptation in the presence of a fluorescent DNA mechanosensor¹¹ or interparticle protocell fusion. Such processes mimic chemically transduced processes found in cell adaptation and cell-to-cell adhesion. Our concept showcases new opportunities to study life-like behaviour via abiotic bioorthogonal chemical and mechanical transformations in synthetic protocells. Furthermore, it reveals a strategy for inducing complex behaviour in adaptive and communicating soft-matter microsystems, and it illustrates how dynamic properties can be upregulated and sustained in micro-compartmentalized media.

smi-miR396b targeted SmGRFs, SmHDT1, and SmMYB37/4 synergistically regulates cell growth and active ingredient accumulation in Salvia miltiorrhiza hairy roots

MIR396b had been cloned and overexpressed in Salvia miltiorrhiza hairy roots. MiR396b targets SmGRFs, SmHDT1, and SmMYB37/4 to regulate cell growth and secondary metabolism in S. miltiorrhiza hairy roots. Danshen (Salvia miltiorrhiza Bunge) is a valuable medicinal herb with two kinds of clinically used natural products, salvianolic acids and tanshinones. miR396 is a conserved microRNA and plays extensive roles in plants. However, it is still unclear how miR396 works in S. miltiorrhiza. In this study, an smi-MIR396b has been cloned from S. miltiorrhiza. Overexpression of miR396b in danshen hairy roots inhibited hairy root growth, reduced salvianolic acid concentration, but enhanced tanshinone accumulation, resulting in the biomass and total salvianolic acids respectively reduced to 55.5 and 72.1% of the control and total tanshinones increased up to 1.91-fold of the control. Applied degradome sequencing, 5'RLM-RACE, and qRT-PCR, 13 targets for miR396b were identified including seven conserved SmGRF1-7 and six novel ones. Comparative transcriptomics and microRNomics analysis together with qRT-PCR results confirmed that miR396b targets SmGRFs, SmHDT1, and SmMYB37/4 to mediate the phytohormone, especially gibberellin signaling pathways and consequentially resulted in the phenotype variation of miR396b-OE hairy roots. Furthermore, miR396b could be activated by methyl jasmonate, abscisic acid, gibberellin, salt, and drought stresses. The findings in this study indicated that smi-miR396b acts as an upstream and central regulator in cell growth and the biosynthesis of tanshinones and salvianolic acids, shedding light on the coordinated regulation of plant growth and biosynthesis of active ingredients in S. miltiorrhiza.

A Sweet Galactose Transfer: Metabolic Oligosaccharide Engineering as a Tool To Study Glycans in Plasmodium Infection

The introduction of chemical reporter groups into glycan structures through metabolic oligosaccharide engineering (MOE) followed by bio-orthogonal ligation is an important tool to study glycosylation. We show the incorporation of synthetic galactose derivatives that bear terminal alkene groups in hepatic cells, with and without infection by Plasmodium berghei parasites, the causative agent of malaria. Additionally, we demonstrated the contribution of GLUT1 to the transport of these galactose derivatives, and observed a consistent increase in the uptake of these compounds going from naïve to P. berghei-infected cells. Finally, we used MOE to study the interplay between Plasmodium parasites and their mosquito hosts, to reveal a possible transfer of galactose building blocks from the latter to the former. This strategy has the potential to provide new insights into Plasmodium glycobiology as well as for the identification and characterization of key glycan structures for further vaccine development.

Environmental decomposition of olefinic cuticular hydrocarbons of Periplaneta americana generates a volatile pheromone that guides social behaviour

Once emitted, semiochemicals are exposed to reactive environmental factors that may alter them, thus disrupting chemical communication. Some species, however, might have adapted to detect environmentally mediated breakdown products of their natural chemicals as semiochemicals. We demonstrate that air, water vapour and ultraviolet (UV) radiation break down unsaturated cuticular hydrocarbons (CHCs) of Periplaneta americana (American cockroach), resulting in the emission of volatile organic compounds (VOCs). In behavioural assays, nymphs strongly avoided aggregating in shelters exposed to the breakdown VOCs from cuticular alkenes. The three treatments (air, water vapour, UV) produced the same VOCs, but at different time-courses and ratios. Fourteen VOCs from UV-exposed CHCs elicited electrophysiological responses in nymph antennae; 10 were identified as 2-nonanone, 1-pentanol, 1-octanol, 1-nonanol, tetradecanal, acetic acid, propanoic acid, butanoic acid, pentanoic acid and hexanoic acid. When short-chain fatty acids were tested as a mix and a blend of the alcohols and aldehyde was tested as a second mix, nymphs exhibited no preference for control or treated shelters. However, nymphs avoided shelters that were exposed to VOCs from the complete 10-compound mix. Conditioned shelters (occupied by cockroaches with faeces and CHCs deposited on the shelters), which are normally highly attractive to nymphs, were also avoided after UV exposure, confirming that breakdown products from deposited metabolites, including CHCs, mediate this behaviour. Our results demonstrate that common environmental agents degrade CHCs into behaviourally active volatile compounds that potentially may serve as necromones or epideictic pheromones, mediating group dissolution.

Mass Spectrometric Detection and Characterization of Metabolites of Gemini Surfactants Used as Gene Delivery Vectors

Gemini surfactants are a class of lipid molecules that have been successfully used in vitro and in vivo as nonviral gene delivery vectors. However, the biological fate of gemini surfactants has not been well investigated. In particular, the metabolism of gemini surfactants after they enter cells as gene delivery vehicles is unknown. In this work, we used a high-resolution quadrupole-Orbitrap mass spectrometry (Q-Exactive) instrument to detect the metabolites of three model gemini surfactants, namely, (a) unsubstituted (16-3-16), (b) with pyridinium head groups (16(Py)-S-2-S-16(Py)), and (c) substituted with a glycyl-lysine di-peptide (16-7N(GK)-16). The metabolites were characterized, and structures were proposed, based on accurate masses and characteristic product ions. The metabolism of the three gemini surfactants was very different as 16-3-16 was not metabolized in PAM 212 cells, whereas 16(Py)-S-2-S-16(Py) was metabolized primarily via phase I reactions, including oxidation and dealkylation, producing metabolites that could be linked to its observed high toxicity. The third gemini surfactant 16-7N(GK)-16 was metabolized mainly via phase II reactions, including methylation, acetylation, glucose conjugation, palmityl conjugation, and stearyl conjugation. The metabolism of gemini surfactants provides insight for future directions in the design and development of more effective gemini surfactants with lower toxicity. The reported approach can also be applied to study the metabolism of other structurally related gemini surfactants.

Co-metabolic enzymes and pathways of 3-phenoxybenzoic acid degradation by Aspergillus oryzae M-4

As an intermediate metabolite of pyrethroids, 3-phenoxybenzoic acid (3-PBA) is more toxic than its parent compounds and has been detected in milk, soil, and human urine. 3-PBA can be metabolized through microbial degradation, but the microbial co-metabolic enzymes and pathways involved in 3-PBA degradation are unclear. This study investigated the enzymes types and possible pathways in the co-metabolic degradation of 3-PBA by Aspergillus oryzae M-4. The enzymes involved in co-metabolic degradation of 3-PBA and its intermediate metabolites were induced, and existed extracellularly and intracellularly except the catechol-degrading enzyme. Inhibitors and inducers of these oxidases were used to examine the enzymes required for co-metabolic degradation of 3-PBA and its intermediate metabolites. 3-PBA is hydroxylated to produce 3-hydroxy-5-phenoxy benzoic acid through the catalytic actions of lignin peroxidase (LiP). Phenol and gallic acid, the metabolites of 3-PBA, are produced via cleavage of an ether bond under the catalytic actions of cytochrome P450 (CYP450) and LiP. Phenol can be converted to catechol by LiP; catechol and gallic acid are cleaved to form long-chain olefin acid or olefin aldehyde by dioxygenase and LiP. In corn flour, some of these enzyme activators such as FeCl₃, 4-cumaric acid, veratryl alcohol and sodium periodate appeared to improve 3-PBA degradation. The results provide a reliable pathway and characteristics for co-metabolic microbial degradation of 3-PBA in food and the environment.

Two new ene-reductases from photosynthetic extremophiles enlarge the panel of old yellow enzymes: CtOYE and GsOYE

Looking for new ene-reductases with uncovered features beneficial for biotechnological applications, by mining genomes of photosynthetic extremophile organisms, we identified two new Old Yellow Enzyme homologues: CtOYE, deriving from the cyanobacterium Chroococcidiopsis thermalis, and GsOYE, from the alga Galdieria sulphuraria. Both enzymes were produced and purified with very good yields and displayed catalytic activity on a broad substrate spectrum by reducing α,β-unsaturated ketones, aldehydes, maleimides and nitroalkenes with good to excellent stereoselectivity. Both enzymes prefer NADPH but demonstrate a good acceptance of NADH as cofactor. CtOYE and GsOYE represent robust biocatalysts showing high thermostability, a wide range of pH optimum and good co-solvent tolerance. High resolution X-ray crystal structures of both enzymes have been determined, revealing conserved features of the classical OYE subfamily as well as unique properties, such as a very long loop entering the active site or an additional C-terminal alpha helix in GsOYE. Not surprisingly, the active site of CtOYE and GsOYE structures revealed high affinity toward anions caught from the mother liquor and trapped in the anion hole where electron-withdrawing groups such as carbonyl group are engaged. Ligands (para-hydroxybenzaldehyde and 2-methyl-cyclopenten-1-one) added on purpose to study complexes of GsOYE were detected in the enzyme catalytic cavity, stacking on top of the FMN cofactor, and support the key role of conserved residues and FMN cofactor in the catalysis.

Myrcene and terpene regulation of TRPV1

Nociceptive Transient Receptor Potential channels such as TRPV1 are targets for treating pain. Both antagonism and agonism of TRP channels can promote analgesia, through inactivation and chronic desensitization. Since plant-derived mixtures of cannabinoids and the Cannabis component myrcene have been suggested as pain therapeutics, we screened terpenes found in Cannabis for activity at TRPV1. We used inducible expression of TRPV1 to examine TRPV1-dependency of terpene-induced calcium flux responses. Terpenes contribute differentially to calcium fluxes via TRPV1 induced by Cannabis-mimetic cannabinoid/terpenoid mixtures. Myrcene dominates the TRPV1-mediated calcium responses seen with terpenoid mixtures. Myrcene-induced calcium influx is inhibited by the TRPV1 inhibitor capsazepine and Myrcene elicits TRPV1 currents in the whole-cell patch-clamp configuration. TRPV1 currents are highly sensitive to internal calcium. When Myrcene currents are evoked, they are distinct from capsaicin responses on the basis of Imax and their lack of shift to a pore-dilated state. Myrcene pre-application and residency at TRPV1 appears to negatively impact subsequent responses to TRPV1 ligands such as Cannabidiol, indicating allosteric modulation and possible competition by Myrcene. Molecular docking studies suggest a non-covalent interaction site for Myrcene in TRPV1 and identifies key residues that form partially overlapping Myrcene and Cannabidiol binding sites. We identify several non-Cannabis plant-derived sources of Myrcene and other compounds targeting nociceptive TRPs using a data mining approach focused on analgesics suggested by non-Western Traditional Medical Systems. These data establish TRPV1 as a target of Myrcene and suggest the therapeutic potential of analgesic formulations containing Myrcene.

Chloroplastic metabolic engineering coupled with isoprenoid pool enhancement for committed taxanes biosynthesis in Nicotiana benthamiana

Production of the anticancer drug Taxol and its precursors in heterologous hosts is more sustainable than extraction from tissues of yew trees or chemical synthesis. Although attempts to engineer the Taxol pathway in microbes have made significant progress, challenges such as functional expression of plant P450 enzymes remain to be addressed. Here, we introduce taxadiene synthase, taxadiene-5α-hydroxylase, and cytochrome P450 reductase in a high biomass plant Nicotiana benthamiana. Using a chloroplastic compartmentalized metabolic engineering strategy, combined with enhancement of isoprenoid precursors, we show that the engineered plants can produce taxadiene and taxadiene-5α-ol, the committed taxol intermediates, at 56.6 μg g-1 FW and 1.3 μg g-1 FW, respectively. In addition to the tools and strategies reported here, this study highlights the potential of Nicotiana spp. as an alternative platform for Taxol production.

Effects of natural ingredients on the shelf life of chicken seasoning

The effects of the natural ingredients Angelica sinensis (AS) and Codonopsis pilosula (CP) on the shelf life of chicken seasoning were investigated. Color differences and sensory evaluation were used to indicate sensory differences. Changes in volatiles were monitored. The rate of increase in the color value a* of the AS and CP samples was lower than that in the control. Rancid flavor appeared later in the AS and CP samples than in the control. The levels of aldehydes, ketones, and alkenes increased during storage. A kinetic model was built based on the proportion of aldehydes (main marker), to predict shelf life. The predicted shelf life at room temperature was 60 days for the control, 114 days for AS, and 89 days for CP. The shelf life of chicken seasoning could be prolonged with AS and CP. This kinetic model can be used to predict the shelf life of chicken seasoning.

Enzymatic hydrolysis of poly(1,4-butylene 2,5-thiophenedicarboxylate) (PBTF) and poly(1,4-butylene 2,5-furandicarboxylate) (PBF) films: A comparison of mechanisms

Enzymatic hydrolysis of poly(1,4-butylene 2,5-thiophenedicarboxylate) (PBTF) and poly(1,4-butylene 2,5-furandicarboxylate) (PBF) by Humicola insolens (HiC) and Thermobifida cellulosilytica (Cut) cutinases is investigated. For the first time, the different depolymerization mechanisms of PBTF (endo-wise scission) and PBF (exo-wise cleavage) has been unveiled and correlated to the chemical structure of the two polyesters.

Biosynthesis of Long Chain Alkyl Diols and Long Chain Alkenols in Nannochloropsis spp. (Eustigmatophyceae)

We investigated potential biosynthetic pathways of long chain alkenols (LCAs), long chain alkyl diols (LCDs), and long chain hydroxy fatty acids (LCHFAs) in Nannochloropsis oceanica and Nannochloropsis gaditana, by combining culturing experiments with genomic and transcriptomic analyses. Incubation of Nannochloropsis spp. in the dark for 1 week led to significant increases in the cellular concentrations of LCAs and LCDs in both species. Consistently, 13C-labelled substrate experiments confirmed that both LCA and LCD were actively produced in the dark from C14-18 fatty acids by either condensation or elongation/hydroxylation, although no enzymatic evidence was found for the former pathway. Nannochloropsis spp. did, however, contain (i) multiple polyketide synthases (PKSs) including one type (PKS-Clade II) that might catalyze incomplete fatty acid elongations leading to the formation of 3-OH-fatty acids, (ii) 3-hydroxyacyl dehydratases (HADs), which can possibly form Δ2/Δ3 monounsaturated fatty acids, and (iii) fatty acid elongases (FAEs) that could elongate 3-OH-fatty acids and Δ2/Δ3 monounsaturated fatty acids to longer products. The enzymes responsible for reduction of the long chain fatty acids to LCDs and LCAs are, however, unclear. A putative wax ester synthase/acyl coenzyme A (acyl-CoA): diacylglycerol acyltransferase is likely to be involved in the esterification of LCAs and LCDs in the cell wall. Our data thus provide useful insights in predicting the biosynthetic pathways of LCAs and LCDs in phytoplankton suggesting a key role of FAE and PKS enzymes.

Evaluation of antioxidant activities of various solvent extract from Sargassum serratifolium and its major antioxidant components

Sargassum serratifolium has been known to contain a high level of meroterpenoids as antioxidant components. We investigated antioxidant activities and active components in various solvent extracts from S. serratifolium. Ethyl acetate, ethanol, and methanol extracts showed relatively strong DPPH, ABTs, and superoxide radical scavenging activities. Hexane and ethyl acetate extract showed the strongest hydroxyl radical and reactive oxygen species (ROS), respectively, scavenging activities. Sargahydroquinoic acid (SHQA), sargachromanol (SCM) and sargaquinoic acid (SQA) were main antioxidant components in S. serratifolium. Ethanol extract showed the highest levels of SHQA, SCM, and SQA which comprised to be 227 ± 6.31 mg/g. SHQA and SCM exhibited stronger antioxidant capacities than SQA based on lower IC50 values in ROS, DPPH, ABTs, and superoxide radical scavenging assays. The result showed that ethanol is the most efficient extracting solvent for the active components from S. serratifolium and the plant has the potential as a natural antioxidant.

Improved dialysis removal of protein-bound uremic toxins by salvianolic acids

BACKGROUND

Indoxyl sulfate (IS) and p-cresyl sulfate (pCS) are two key protein-bound uremic toxins that accumulate in patients with end-stage renal disease. IS and pCS cannot be efficiently removed by conventional hemodialysis because they are highly bound to proteins. One promising means to optimize the removal of protein-bound uremic toxins involves using binding competitors to liberate uremic toxins from protein-binding partners.

PURPOSE

In this study, we try to identify potential binding competitors that can enhance the dialysis removal of IS and pCS in natural compounds of phytomedicine.

METHODS

We employed microdialysis to evaluate whether Danhong injection (DHI) and its salvianolic acids can increase the free fractions of IS and pCS and thus improve their dialysis efficiency in vitro. Furthermore, we confirmed the positive effects of DHI and salvianolic acids in vivo on chronic kidney disease model rats in which IS and pCS had heavily accumulated.

RESULTS

DHI significantly increased the dialysis efficiency of IS and pCS by 99.13% and 142.00% in vitro (10-fold dilution), respectively, and by 135.61% and 272.13% in vivo (4.16 ml/kg). Salvianolic acids including lithospermic acid (LA), salvianolic acid A (SaA), tanshinol (DSS), caffeic acid (CA), salvianolic acid B (SaB), protocatechuic aldehyde (PA) and rosmarinic acid (RA) significantly enhanced the dialysis removal of IS and pCS in a concentration-dependent manner. LA, the best competitor of the tested salvianolic acids, increased dialysis efficiency levels of IS and pCS by 197.23% and 198.31% in vitro (400 μM), respectively, and by 119.55% and 127.56% in vivo (24.69 mg/kg).

CONCLUSION

The removal of protein-bound uremic toxins IS and pCS using DHI or salvianolic acids as protein-bound competitors is superior to previously reported strategies and drugs and may contribute to clinical hemodialysis therapeutic practice.

A chemoselective strategy for late-stage functionalization of complex small molecules with polypeptides and proteins

Conjugates between proteins and small molecules enable access to a vast chemical space that is not achievable with either type of molecule alone; however, the paucity of specific reactions capable of functionalizing proteins and natural products presents a formidable challenge for preparing conjugates. Here we report a strategy for conjugating electron-rich (hetero)arenes to polypeptides and proteins. Our bioconjugation technique exploits the electrophilic reactivity of an oxidized selenocysteine residue in polypeptides and proteins, and the electron-rich character of certain small molecules to provide bioconjugates in excellent yields under mild conditions. This conjugation chemistry enabled the synthesis of peptide-vancomycin conjugates without the prefunctionalization of vancomycin. These conjugates have an enhanced in vitro potency for resistant Gram-positive and Gram-negative pathogens. Additionally, we show that a 6 kDa affibody protein and a 150 kDa immunoglobulin-G antibody could be modified without diminishing bioactivity.

A genetically-encoded synthetic self-assembled multienzyme complex of lipase and P450 fatty acid decarboxylase for efficient bioproduction of fatty alkenes

We develop an efficient and economic cascade multienzymes for fatty alkene bioproduction based on the lipase hydrolysis coupled to the P450 decarboxylation in the form of multiple enzyme complex. One step preparation of a multienzyme complex was based on a mixture of cell extracts including dockerin-enzyme fusions and one cohesin-cellulose binding module (CBM) fusion through high specific interaction of dockerin and cohesin. Simultaneously, the CBM was bound to cellulose carrier to form co-immobilized multienzyme. The key factors affecting overall efficiency of alkene bioproduction including substrate channeling of hydrolysis and decarboxylation, the ratio and position of two enzymes, stability were all addressed by genetically engineering of the synthetic CBM-cohesin fusions. The multienzymes exhibited more than 9.2 fold enhancement in initial reaction rate and much higher conversion yields (69%-72%) compared to mixture of free enzyme counterpart. The enzymatic cascade based multienzymes could efficiently convert renewable triglycerides to alkenes.

Chemical fingerprinting of single glandular trichomes of Cannabis sativa by Coherent anti-Stokes Raman scattering (CARS) microscopy

BACKGROUND

Cannabis possesses a rich spectrum of phytochemicals i.e. cannabinoids, terpenes and phenolic compounds of industrial and medicinal interests. Most of these high-value plant products are synthesised in the disk cells and stored in the secretory cavity in glandular trichomes. Conventional trichome analysis was so far based on optical microscopy, electron microscopy or extraction based methods that are either limited to spatial or chemical information. Here we combine both information to obtain the spatial distribution of distinct secondary metabolites on a single-trichome level by applying Coherent anti-Stokes Raman scattering (CARS), a microspectroscopic technique, to trichomes derived from sepals of a drug- and a fibre-type.

RESULTS

Hyperspectral CARS imaging in combination with a nonlinear unmixing method allows to identify and localise Δ⁹-tetrahydrocannabinolic acid (THCA) in the secretory cavity of drug-type trichomes and cannabidiolic acid (CBDA)/myrcene in the secretory cavity of fibre-type trichomes, thus enabling an easy discrimination between high-THCA and high-CBDA producers. A unique spectral fingerprint is found in the disk cells of drug-type trichomes, which is most similar to cannabigerolic acid (CBGA) and is not found in fibre-type trichomes. Furthermore, we differentiate between different cell types by a combination of CARS with simultaneously acquired two-photon fluorescence (TPF) of chlorophyll a from chloroplasts and organic fluorescence mainly arising from cell walls enabling 3D visualisation of the essential oil distribution and cellular structures.

CONCLUSION

Here we demonstrate a label-free and non-destructive method to analyse the distribution of secondary metabolites and distinguish between different cell and chemo-types with high spatial resolution on a single trichome. The record of chemical fingerprints of single trichomes offers the possibility to optimise growth conditions as well as guarantee a direct process control for industrially cultivated medicinal Cannabis plants. Moreover, this method is not limited to Cannabis related issues but can be widely implemented for optimising and monitoring all kinds of natural or biotechnological production processes with simultaneous spatial and chemical information.

Redox Signaling by Reactive Electrophiles and Oxidants

The concept of cell signaling in the context of nonenzyme-assisted protein modifications by reactive electrophilic and oxidative species, broadly known as redox signaling, is a uniquely complex topic that has been approached from numerous different and multidisciplinary angles. Our Review reflects on five aspects critical for understanding how nature harnesses these noncanonical post-translational modifications to coordinate distinct cellular activities: (1) specific players and their generation, (2) physicochemical properties, (3) mechanisms of action, (4) methods of interrogation, and (5) functional roles in health and disease. Emphasis is primarily placed on the latest progress in the field, but several aspects of classical work likely forgotten/lost are also recollected. For researchers with interests in getting into the field, our Review is anticipated to function as a primer. For the expert, we aim to stimulate thought and discussion about fundamentals of redox signaling mechanisms and nuances of specificity/selectivity and timing in this sophisticated yet fascinating arena at the crossroads of chemistry and biology.

Molecular Basis for Olefin Rearrangement in the Gephyronic Acid Polyketide Synthase

Polyketide synthases (PKS) are a rich source of natural products of varied chemical composition and biological significance. Here, we report the characterization of an atypical dehydratase (DH) domain from the PKS pathway for gephyronic acid, an inhibitor of eukaryotic protein synthesis. Using a library of synthetic substrate mimics, the reaction course, stereospecificity, and tolerance to non-native substrates of GphF DH1 are probed via LC-MS analysis. Taken together, the studies establish GphF DH1 as a dual-function dehydratase/isomerase that installs an odd-to-even double bond and yields a product consistent with the isobutenyl terminus of gephyronic acid. The studies also reveal an unexpected C2 epimerase function in catalytic turnover with the native substrate. A 1.55-Å crystal structure of GphF DH1 guided mutagenesis experiments to elucidate the roles of key amino acids in the multistep DH1 catalysis, identifying critical functions for leucine and tyrosine side chains. The mutagenesis results were applied to add a secondary isomerase functionality to a nonisomerizing DH in the first successful gain-of-function engineering of a PKS DH. Our studies of GphF DH1 catalysis highlight the versatility of the DH active site and adaptation for a specific catalytic outcome with a specific substrate.

Engineered bidirectional promoters enable rapid multi-gene co-expression optimization

Numerous synthetic biology endeavors require well-tuned co-expression of functional components for success. Classically, monodirectional promoters (MDPs) have been used for such applications, but MDPs are limited in terms of multi-gene co-expression capabilities. Consequently, there is a pressing need for new tools with improved flexibility in terms of genetic circuit design, metabolic pathway assembly, and optimization. Here, motivated by nature's use of bidirectional promoters (BDPs) as a solution for efficient gene co-expression, we generate a library of 168 synthetic BDPs in the yeast Komagataella phaffii (syn. Pichia pastoris), leveraging naturally occurring BDPs as a parts repository. This library of synthetic BDPs allows for rapid screening of diverse expression profiles and ratios to optimize gene co-expression, including for metabolic pathways (taxadiene, β-carotene). The modular design strategies applied for creating the BDP library could be relevant in other eukaryotic hosts, enabling a myriad of metabolic engineering and synthetic biology applications.

Heterologous Expression of Mycobacterium Alkene Monooxygenases in Gram-Positive and Gram-Negative Bacterial Hosts

Alkene monooxygenases (MOs) are soluble di-iron-containing enzymes found in bacteria that grow on alkenes. Here, we report improved heterologous expression systems for the propene MO (PmoABCD) and ethene MO (EtnABCD) from Mycobacterium chubuense strain NBB4. Strong functional expression of PmoABCD and EtnABCD was achieved in Mycobacterium smegmatis mc2155, yielding epoxidation activities (62 and 27 nmol/min/mg protein, respectively) higher than any reported to date for heterologous expression of a di-iron MO system. Both PmoABCD and EtnABCD were specialized for the oxidation of gaseous alkenes (C2 to C4), and their activity was much lower on liquid alkenes (C5 to C8). Despite intensive efforts to express the complete EtnABCD enzyme in Escherichia coli, this was not achieved, although recombinant EtnB and EtnD proteins could be purified individually in soluble form. The biochemical function of EtnD as an oxidoreductase was confirmed (1.36 μmol cytochrome c reduced/min/mg protein). Cloning the EtnABCD gene cluster into Pseudomonas putida KT2440 yielded detectable epoxidation of ethene (0.5 nmol/min/mg protein), and this could be stimulated (up to 1.1 nmol/min/mg protein) by the coexpression of cpn60 chaperonins from either Mycobacterium spp. or E. coli Successful expression of the ethene MO in a Gram-negative host was validated by both whole-cell activity assays and peptide mass spectrometry of induced proteins seen on SDS-PAGE gels.IMPORTANCE Alkene MOs are of interest for their potential roles in industrial biocatalysis, most notably for the stereoselective synthesis of epoxides. Wild-type bacteria that grow on alkenes have high activities for alkene oxidation but are problematic for biocatalysis, since they tend to consume the epoxide products. Using recombinant biocatalysts is the obvious alternative, but a major bottleneck is the low activities of recombinant alkene MOs. Here, we provide new high-activity recombinant biocatalysts for alkene oxidation, and we provide insights into how to further improve these systems.

Enhancement of methane production from 1-hexadecene by additional electron donors

1-Hexadecene-contaminated wastewater is produced in oil refineries and can be treated in methanogenic bioreactors, although generally at low conversion rates. In this study, a microbial culture able to degrade 1-hexadecene was enriched, and different stimulation strategies were tested for enhancing 1-hexadecene conversion to methane. Seven and three times faster methane production was obtained in cultures stimulated with yeast extract or lactate, respectively, while cultures amended with crotonate lost the ability to degrade 1-hexadecene. Methane production from 1-hexadecene was not enhanced by the addition of extra hydrogenotrophic methanogens. Bacteria closely related to Syntrophus and Smithella were detected in 1-hexadecene-degrading cultures, but not in the ones amended with crotonate, which suggests the involvement of these bacteria in 1-hexadecene degradation. Genes coding for alkylsuccinate synthase alpha-subunit were detected in cultures degrading 1-hexadecene, indicating that hydrocarbon activation may occur by fumarate addition. These findings are novel and show that methane production from 1-hexadecene is improved by the addition of yeast extract or lactate. These extra electron donors may be considered as a potential bioremediation strategy of oil-contaminated sites with bioenergy generation through methane production.

Electron ionization mass spectrometry fragmentation and multiple reaction monitoring quantification of bacterial metabolites of the sea ice biomarker proxy IP25 in Arctic sediments

RATIONALE

3,9,13-Trimethyl-6-(1,5-dimethylhexyl)tetradecan-1,2-diol and 2,8,12-trimethyl-5-(1,5-dimethylhexyl)tridecanoic acid appear to be produced during the bacterial metabolism of IP₂₅ , a highly branched isoprenoid lipid often employed for past Arctic sea ice reconstruction. Characterization and quantification of these metabolites in sediments are essential to determine if bacterial degradation may exert a significant influence on IP₂₅ -based palaeo sea ice reconstructions.

METHODS

Electron ionization mass spectrometry (EIMS) fragmentation pathways of 3,9,13-trimethyl-6-(1,5-dimethylhexyl)tetradecan-1,2-diol and 2,8,12-trimethyl-5-(1,5-dimethylhexyl)tridecanoic acid trimethylsilyl (TMS) derivatives were investigated. These pathways were deduced by: (i) low-energy collision-induced dissociation (CID) gas chromatography/tandem mass spectrometry (GC/MS/MS), (ii) accurate mass measurement, and (iii) deuterium labelling.

RESULTS

CID-MS/MS analyses, accurate mass measurement and deuterium-labelling experiments enabled us to elucidate the EIMS fragmentations of 3,9,13-trimethyl-6-(1,5-dimethylhexyl)tetradecan-1,2-diol and 2,8,12-trimethyl-5-(1,5-dimethylhexyl)tridecanoic acid TMS derivatives. Some specific fragment ions useful in addition to chromatographic retention times for further characterization could be identified. As an application of some of the described fragmentations, the TMS derivatives of these metabolites were characterized and quantified in MRM mode in different Arctic sediments.

CONCLUSIONS

EIMS fragmentations of 3,9,13-trimethyl-6-(1,5-dimethylhexyl)tetradecan-1,2-diol and 2,8,12-trimethyl-5-(1,5-dimethylhexyl)tridecanoic acid TMS derivatives exhibit specific fragment ions, which appear to be very useful for the quantification of these bacterial metabolites of the palaeo tracer IP₂₅ in sediments.

Taxadiene-5α-ol is a minor product of CYP725A4 when expressed in Escherichia coli

CYP725A4 is a P450 enzyme from Taxus cuspidata that catalyzes the formation of taxadiene-5α-ol (T5α-ol) from taxadiene in paclitaxel biosynthesis. Past attempts expressing CYP725A4 in heterologous hosts reported the formation of 5(12)-oxa-3(11)-cyclotaxane (OCT) and/or 5(11)-oxa-3(11)-cyclotaxane (iso-OCT) instead of, or in addition to, T5α-ol. Here, we report that T5α-ol is produced as a minor product by Escherichia coli expressing both taxadiene synthase and CYP725A4. The major products were OCT and iso-OCT, while trace amounts of unidentified monooxygenated taxanes were also detected by gas chromatography-mass spectrometry. Since OCT and iso-OCT had not been found in nature, we tested the hypothesis that protein-protein interaction of CYP725A4 with redox partners, such as cytochrome P450 reductase (CPR) and cytochrome b5, may affect the products formed by CYP725A4, possibly favoring the formation of T5α-ol over OCT and iso-OCT. Our results show that coexpression of CYP725A4 with CPR from different organisms did not change the relative ratios of OCT, iso-OCT, and T5α-ol, while cytochrome b5 decreased overall levels of the products formed. Although unsuccessful in finding conditions that promote T5α-ol formation over other products, we used our results to clarify conflicting claims in the literature and discuss other possible approaches to produce paclitaxel via metabolic and enzyme engineering.

SmJAZ8 acts as a core repressor regulating JA-induced biosynthesis of salvianolic acids and tanshinones in Salvia miltiorrhiza hairy roots

Jasmonates (JAs) are important plant hormones that regulate a variety of plant development and defense processes, including biosynthesis of secondary metabolites. The JASMONATE ZIM DOMAIN (JAZ) proteins act as negative regulators in the JA signaling pathways of plants. We first verified that methyl jasmonate (MeJA) enhanced the accumulation of both salvianolic acids and tanshinones in Salvia miltiorrhiza (Danshen) hairy roots by inducing the expression of their biosynthetic pathway genes. Nine JAZ genes were cloned from Danshen and their expression levels in hairy roots were all increased by treatment with MeJA. When analyzed in detail, however, SmJAZ8 showed the strongest expression in the induced hairy roots. Overexpression or RNAi of SmJAZ8 deregulated or up-regulated the yields of salvianolic acids and tanshinones in the MeJA-induced transgenic hairy roots, respectively, and transcription factors and biosynthetic pathway genes showed an expression pattern that mirrored the production of the compounds. Genetic transformation of SmJAZ8 altered the expression of other SmJAZ genes, suggesting evidence of crosstalk occurring in JAZ-regulated secondary metabolism. Furthermore, the transcriptome analysis revealed a primary-secondary metabolism balance regulated by SmJAZ8. Altogether, we propose a novel role for SmJAZ8 as a negative feedback loop controller in the JA-induced biosynthesis of salvianolic acids and tanshinones.

Characterization of two styrene monooxygenases from marine microbes

Styrene monooxygenases (SMOs) are highly stereoselective enzymes that catalyze the formation of chiral epoxides as versatile building blocks. To expand the enzyme toolbox, two bacterial SMOs were identified from the genome of marine microbes Paraglaciecola agarilytica NO2 and Marinobacterium litorale DSM 23545, and heterologously expressed in Escherichia coli in soluble form. Both of the resulting whole-cell biocatalysts exhibited maximal activity at 30 °C and pH 8.0. They catalyzed the sulfoxidation reactions, and the epoxidation of both conjugated and unconjugated styrene derivatives with up to >99%ee. MlSMO displayed higher activity toward most substrates tested. Compared to an established SMO from Pseudomonas species (PsSMO), MlSMO achieved 3.0-, 3.4- and 2.6-fold conversions for substrates styrene, cinnamyl alcohol and 4-vinyl-2, 3-dihydrobenzofuran, respectively.

Molecular Pharmacology of Rosmarinic and Salvianolic Acids: Potential Seeds for Alzheimer's and Vascular Dementia Drugs

Both caffeic acid and 3,4-dihydroxyphenyllactic acid (danshensu) are synthesized through two distinct routs of the shikimic acid biosynthesis pathway. In many plants, especially the rosemary and sage family of Lamiaceae, these two compounds are joined through an ester linkage to form rosmarinic acid (RA). A further structural diversity of RA derivatives in some plants such as Salvia miltiorrhiza Bunge is a form of RA dimer, salvianolic acid-B (SA-B), that further give rise to diverse salvianolic acid derivatives. This review provides a comprehensive perspective on the chemistry and pharmacology of these compounds related to their potential therapeutic applications to dementia. The two common causes of dementia, Alzheimer's disease (AD) and stroke, are employed to scrutinize the effects of these compounds in vitro and in animal models of dementia. Key pharmacological mechanisms beyond the common antioxidant and anti-inflammatory effects of polyphenols are highlighted with emphasis given to amyloid beta (Aβ) pathologies among others and neuronal regeneration from stem cells.

Identification and functional analysis of two P450 enzymes of Gossypium hirsutum involved in DMNT and TMTT biosynthesis

The homoterpenes (3E)-4,8-dimethyl-1,3,7-nonatriene (DMNT) and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT) are major herbivore-induced plant volatiles that can attract predatory or parasitic arthropods to protect injured plants from herbivore attack. In this study, DMNT and TMTT were confirmed to be emitted from cotton (Gossypium hirsutum) plants infested with chewing caterpillars or sucking bugs. Two CYP genes (GhCYP82L1 and GhCYP82L2) involved in homoterpene biosynthesis in G. hirsutum were newly identified and characterized. Yeast recombinant expression and enzyme assays indicated that the two GhCYP82Ls are both responsible for the conversion of (E)-nerolidol to DMNT and (E,E)-geranyllinalool to TMTT. The two heterologously expressed proteins without cytochrome P450 reductase fail to convert the substrates to homoterpenes. Quantitative real-time PCR (qPCR) analysis suggested that the two GhCYP82L genes were significantly up-regulated in leaves and stems of G. hirsutum after herbivore attack. Subsequently, electroantennogram recordings showed that electroantennal responses of Microplitis mediator and Peristenus spretus to DMNT and TMTT were both dose dependent. Laboratory behavioural bioassays showed that females of both wasp species responded positively to DMNT and males and females of M. mediator could be attracted by TMTT. The results provide a better understanding of homoterpene biosynthesis in G. hirsutum and of the potential influence of homoterpenes on the behaviour of natural enemies, which lay a foundation to study genetically modified homoterpene biosynthesis and its possible application in agricultural pest control.