Vanadium-dependent Haloperoxidases Research Articles

Enantioselectivity in Vanadium-Dependent Haloperoxidases of Different Marine Sources for Sulfide Oxidation to Sulfoxides.

This study explores the reasons behind the variations in the enantioselectivity of the sulfoxidation of methyl phenyl sulfide by marine-derived vanadium-dependent haloperoxidases (VHPOs). Twelve new VHPOs of marine organisms were overexpressed, purified, and tested for their ability to oxidize sulfide. Most of these marine enzymes exhibited nonenantioselective behavior, underscoring the uniqueness of AnVBPO from the brown seaweed Ascophyllum nodosum and CpVBPO from the red seaweed Corallina pilulifera, which produce (R)- and (S)-sulfoxides, respectively. The enantioselective sulfoxidation pathway is likely due to direct oxygen transfer within the VHPO active site. This was demonstrated through molecular docking and molecular dynamics simulations, which revealed differences in the positioning of sulfide within AnVBPO and CpVBPO, thus explaining their distinct enantioselectivities. Nonenantioselective VHPOs probably follow a different oxidation pathway, initiating with sulfide oxidation to form a positively charged radical. Further insights were gained from studying the catalytic effect of VO43- on H2O2-driven sulfoxidation. This research improves the understanding of VHPO-mediated sulfoxidation and aids in developing biocatalysts for sulfoxide synthesis.

N-Halogenation by Vanadium-Dependent Haloperoxidases Enables 1,2,4-Oxadiazole Synthesis.

Nitrogen-containing compounds are valuable synthetic intermediates and targets in nearly every chemical industry. While methods for nitrogen-carbon and nitrogen-heteroatom bond formation have primarily relied on nucleophilic nitrogen atom reactivity, molecules containing nitrogen-halogen bonds allow for electrophilic or radical reactivity modes at the nitrogen center. Despite the growing synthetic utility of nitrogen-halogen bond-containing compounds, selective catalytic strategies for their synthesis are largely underexplored. We recently discovered that the vanadium-dependent haloperoxidase (VHPO) class of enzymes are a suitable biocatalyst platform for nitrogen-halogen bond formation. Herein, we show that VHPOs perform selective halogenation of a range of substituted benzamidine hydrochlorides to produce the corresponding N'-halobenzimidamides. This biocatalytic platform is applied to the synthesis of 1,2,4-oxadiazoles from the corresponding N-acylbenzamidines in high yield and with excellent chemoselectivity. Finally, the synthetic applicability of this biotechnology is demonstrated in an extension to nitrogen-nitrogen bond formation and the chemoenzymatic synthesis of the Duchenne muscular dystrophy drug, ataluren.

N‐Halogenation by Vanadium‐Dependent Haloperoxidases Enables 1,2,4‐Oxadiazole Synthesis

Nitrogen‐containing compounds are valuable synthetic intermediates and targets in nearly every chemical industry. While methods for nitrogen‐carbon and nitrogen‐heteroatom bond formation have primarily relied on nucleophilic nitrogen atom reactivity, molecules containing nitrogen‐halogen bonds allow for electrophilic or radical reactivity modes at the nitrogen center. Despite the growing synthetic utility of nitrogen‐halogen bond‐containing compounds, selective catalytic strategies for their synthesis are largely underexplored. We recently discovered that the vanadium‐dependent haloperoxidase (VHPO) class of enzymes are a suitable biocatalyst platform for nitrogen‐halogen bond formation. Herein, we show that VHPOs perform selective halogenation of a range of substituted benzamidine hydrochlorides to produce the corresponding N’‐halobenzimidamides. This biocatalytic platform is applied to the synthesis of 1,2,4‐oxadiazoles from the corresponding N‐acylbenzamidines in high yield and with excellent chemoselectivity. Finally, the synthetic applicability of this biotechnology is demonstrated in an extension to nitrogen‐nitrogen bond formation and the chemoenzymatic synthesis of the Duchenne muscular dystrophy drug, ataluren.

Identification of differential gene expression related to reproduction in the sporophytes of Saccharina japonica.

Saccharina japonica, a significant brown macroalga in the Pacific Ocean, serves as a food source and industrial material. In aquaculture, collecting mature sporophytes for seedling production is essential but challenging due to environmental changes. In this study, transcriptomic analysis of vegetative and sorus tissues was done to identify differentially expressed genes (DEGs) and enhance our understanding of sorus formation regulation in S. japonica. KEGG pathway and Gene Otology (GO) analysis revealed that upregulated DEGs were involved in folate biosynthesis, riboflavin metabolism, and amino acid biosynthesis. In addition, the upregulation of genes associated with cell wall remodeling, such as mannuronan C-5-epimerases, vanadium-dependent haloperoxidases, and NADPH oxidase, was observed in sorus parts. Meanwhile, downregulated DEGs in sorus portions included genes related to chloroplast function. These findings will help us understand the regulatory mechanisms behind sorus formation in S. japonica and extracellular matrix remodeling in brown algae.

Vanadium-dependent haloperoxidases from diverse microbes halogenate exogenous alkyl quinolone quorum sensing signals.

Site-selective vanadium-dependent haloperoxidases (VHPOs) are a unique enzyme family that catalyze selective halogenation reactions previously characterized within bacterial natural product biosynthetic pathways. However, the broader chemical roles and biological distribution of these halogenases remains to be explored. Using bioinformatic methods, we have defined a VHPO subfamily that regioselectively brominates alkyl quinolone (AQ) quorum sensing molecules. In vitro AQ halogenation activity was demonstrated from phylogenetically distinct bacteria lacking established AQ biosynthetic pathways and sourced from diverse environments. AQ-VHPOs show high sequence and biochemical similarities with negligible genomic synteny or biosynthetic gene cluster co-localization. Exposure of VHPO-containing microbes to synthetic AQs or established bacterial producers identifies the chemical and spatial response to subvert their bacteriostatic effects. The characterization of novel homologs from bacterial taxa without previously demonstrated vanadium enzymology suggests VHPO-mediated AQ bromination is a niche to manipulate the chemical ecology of microbial communities.

Phytase from Aspergillus oryzae SBS50: Biocatalytic reduction of anti-nutritional factor and exhibiting vanadium-dependent haloperoxidase activity

Phytases are valuable industrial enzymes widely used in food and feed production for monogastric animals. The purpose of this research is to study the possibility of employing solid-state fermentation (SSF) for phytase production by Aspergillus oryzae SBS50 using mixed substrates. Medium components for improvement of phytase production were optimized using ‘one variable at a time’ method. Optimization resulted in an overall 2.1 times increase in phytase production (506.12 U/g DMR) at 30 °C, pH 5.0 and moisture ratio of 1:4 supplemented with 0.75% ammonium sulphate. There was reduction in phytase production with reduction in water activity. The phytic acid was extracted from flours using hydrochloric acid (HCl) and trichloroacetic acid (TCA). Higher phytic acid content was extracted from wheat flour (3881.6 μg/g), among all the tested flours by HCl extraction method. Fungal phytase was used in the dephytinization of flours. Phytase supplementation enhanced the release of inorganic phosphate, reducing sugars and soluble proteins from all the flours. Treatment of different cereal flours with Aspergillus oryzae phytase resulted in 90–97% reduction in phytic acid content after 24h. A significant amount of inorganic phosphorus was released from wheat flour (10.42 mg/g), pearl millet flour (9.1 mg/g) followed by gram flour (6.2 mg/g) and rice flour (3.9 mg/g). The addition of vanadium resulted in the catalytic conversion of phytase into haloperoxidase, as well as the suppression of phytase activity. This study revealed that phytase from A. oryzae SBS50 can be utilized to improve the nutritional content of cereal-based meals and food products in the food processing sectors. Furthermore, semisynthetic haloperoxidase could be useful in various biotechnological applications.

Catalytic Potential of Pyrazolone Based Dioxidomolybdenum(VI) Complexes for Multicomponent Biginelli Reactions, Epoxidation of Olefins and Oxidative Bromination of Phenol Derivatives

AbstractThree different types of dioxidomolybdenum(VI) complexes of 4‐acetyl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (Hmp, I)), 3‐methyl‐1‐phenyl‐4‐propionyl‐5‐pyrazolone (Hpp, II), 4‐butyryl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (Hbutp, III), and 4‐isobutyryl‐3‐methyl‐1‐phenyl‐5‐pyrazolone (isobutp, IV) have been isolated and characterized by various spectroscopic (FT‐IR, UV/Vis, 1H and 13C NMR) techniques, thermal analysis and single crystal X‐ray analysis. These complexes adopt a distorted six‐coordinate octahedral geometry where ligands act as bidentate, coordinating through the two O atoms. These complexes have been used as catalysts to explore a single pot multicomponent (benzaldehyde or its derivatives, urea/thiourea and ethyl acetoacetate/phenyl acetoacatate) Biginelli reaction producing biologically active 3,4‐dihydropyrimidin‐2‐(1H)‐one and 3,4‐dihydropyrimidin‐2‐(1H)‐thione based biomolecules under solvent‐free conditions. Presence of H2O2 improves the yield of dihydropyrimidin‐2‐(1H)‐one but it acts as poison for the later molecule. Epoxidation of internal and terminal alkenes mainly resulted in the formation of the corresponding epoxide. The catalytic oxidative bromination of thymol, a reaction facilitated by vanadium dependent haloperoxidases, resulted in the formation of three product namely 2‐bromothymol, 4‐bromothymol and 2,4‐bromothymol. Other phenol derivatives have also been brominated effectively.

Heterologous Expression and Biochemical Characterization of a New Chloroperoxidase Isolated from the Deep-Sea Hydrothermal Vent Black Yeast Hortaea werneckii UBOCC-A-208029.

The initiation of this study relies on a targeted genome-mining approach to highlight the presence of a putative vanadium-dependent haloperoxidase-encoding gene in the deep-sea hydrothermal vent fungus Hortaea werneckii UBOCC-A-208029. To date, only three fungal vanadium-dependent haloperoxidases have been described, one from the terrestrial species Curvularia inaequalis, one from the fungal plant pathogen Botrytis cinerea, and one from a marine derived isolate identified as Alternaria didymospora. In this study, we describe a new vanadium chloroperoxidase from the black yeast H. werneckii, successfully cloned and overexpressed in a bacterial host, which possesses higher affinity for bromide (Km = 26µM) than chloride (Km = 237mM). The enzyme was biochemically characterized, and we have evaluated its potential for biocatalysis by determining its stability and tolerance in organic solvents. We also describe its potential three-dimensional structure by building a model using the AlphaFold 2 artificial intelligence tool. This model shows some conservation of the 3D structure of the active site compared to the vanadium chloroperoxidase from C. inaequalis but it also highlights some differences in the active site entrance and the volume of the active site pocket, underlining its originality.

A Proteomic Analysis for the Red Seaweed Asparagopsis taxiformis.

The red seaweed Asparagopsis taxiformis is a promising ruminant feed additive with anti-methanogenic properties that could contribute to global climate change solutions. Genomics has provided a strong foundation for in-depth molecular investigations, including proteomics. Here, we investigated the proteome of A. taxiformis (Lineage 6) in both sporophyte and gametophyte stages, using soluble and insoluble extraction methods. We identified 741 unique non-redundant proteins using a genome-derived database and 2007 using a transcriptome-derived database, which included numerous proteins predicted to be of fungal origin. We further investigated the genome-derived proteins to focus on seaweed-specific proteins. Ontology analysis indicated a relatively large proportion of ion-binding proteins (i.e., iron, zinc, manganese, potassium and copper), which may play a role in seaweed heavy metal tolerance. In addition, we identified 58 stress-related proteins (e.g., heat shock and vanadium-dependent haloperoxidases) and 44 photosynthesis-related proteins (e.g., phycobilisomes, photosystem I, photosystem II and ATPase), which were in general more abundantly identified from female gametophytes. Forty proteins were predicted to be secreted, including ten rhodophyte collagen-alpha-like proteins (RCAPs), which displayed overall high gene expression levels. These findings provide a comprehensive overview of expressed proteins in A. taxiformis, highlighting the potential for targeted protein extraction and functional characterisation for future biodiscovery.

Identification and Characterization of the Haloperoxidase VPO-RR from Rhodoplanes roseus by Genome Mining and Structure-Based Catalytic Site Mapping

Halogenating enzymes have evolved in considerable mechanistic diversity. The apparent need for secondary metabolism coincides with the current need to introduce halogens in synthetic products. The potential of halogenating enzymes and, especially, vanadate-dependent haloperoxidases has been insufficiently exploited for synthetic purposes. In this work, we identified potential halogenase sequences by screening algal, fungal, and protobacterial sequence databases, structural modeling of putative halogenases, and mapping and comparing active sites. In a final step, individual haloperoxidases were expressed and kinetically characterized. A vanadate-dependent haloperoxidase from Rhodoplanes roseus was heterologously expressible by E. coli and could be purified to homogeneity. The kinetic data revealed a higher turnover number than the known VClPO-CI and no inhibitory effect from bromide, rendering this enzyme a promising biocatalyst. Other predicted haloperoxidases were not expressed successfully yet but these enzymes were predicted to be present in a wide taxonomic variety.

Structural Basis of Stereospecific Vanadium-Dependent Haloperoxidase Family Enzymes in Napyradiomycin Biosynthesis.

Vanadium-dependent haloperoxidases (VHPOs) from Streptomyces bacteria differ from their counterparts in fungi, macroalgae, and other bacteria by catalyzing organohalogenating reactions with strict regiochemical and stereochemical control. While this group of enzymes collectively uses hydrogen peroxide to oxidize halides for incorporation into electron-rich organic molecules, the mechanism for the controlled transfer of highly reactive chloronium ions in the biosynthesis of napyradiomycin and merochlorin antibiotics sets the Streptomyces vanadium-dependent chloroperoxidases apart. Here we report high-resolution crystal structures of two homologous VHPO family members associated with napyradiomycin biosynthesis, NapH1 and NapH3, that catalyze distinctive chemical reactions in the construction of meroterpenoid natural products. The structures, combined with site-directed mutagenesis and intact protein mass spectrometry studies, afforded a mechanistic model for the asymmetric alkene and arene chlorination reactions catalyzed by NapH1 and the isomerase activity catalyzed by NapH3. A key lysine residue in NapH1 situated between the coordinated vanadate and the putative substrate binding pocket was shown to be essential for catalysis. This observation suggested the involvement of the ε-NH2, possibly through formation of a transient chloramine, as the chlorinating species much as proposed in structurally distinct flavin-dependent halogenases. Unexpectedly, NapH3 is modified post-translationally by phosphorylation of an active site His (τ-pHis) consistent with its repurposed halogenation-independent, α-hydroxyketone isomerase activity. These structural studies deepen our understanding of the mechanistic underpinnings of VHPO enzymes and their evolution as enantioselective biocatalysts.

Atomically dispersed V-N-C catalyst with saturated coordination effect for boosting electrochemical oxygen reduction

Single atom catalysts (SACs) exhibit impressive catalytic activity for various reactions due to low coordination environment and tunable electronic structures, attracting increasing attention. However, it is big challenge to develop transition-metal-based SACs for oxygen reduction reaction (ORR) with high stability. Bioinspired by the structure and mechanism of vanadium-dependent haloperoxidase, we herein demonstrate that saturated coordination could boost ORR activity of atomically dispersed V-N-C catalyst combining DFT prediction and experimental verification. Spontaneous axial OH coordination to V-N-C catalyst in alkaline electrolyte not only optimizes the adsorption interaction for key intermediates to boost ORR activity, but also keeps vanadium atom at the highest valence against Fenton activity to improve the stability. The as-designed catalyst exhibits half-wave potential of 0.858 V vs. RHE for ORR, comparable to the commercial Pt/C benchmark. This work provides a proof-of-concept design of SACs and broadens the horizon of its potential applications.

Investigating the Role of Vanadium-Dependent Haloperoxidase Enzymology in Microbial Secondary Metabolism and Chemical Ecology.

ABSTRACTThe chemical diversity of natural products is established by an elegant network of biosynthetic machinery and controlled by a suite of intracellular and environmental cues. Advances in genomics, transcriptomics, and metabolomics have provided useful insight to understand how organisms respond to abiotic and biotic factors to adjust their chemical output; this has permitted researchers to begin asking bigger-picture questions regarding the ecological significance of these molecules to the producing organism and its community. Our lab is motivated by understanding how select microbes construct and manipulate bioactive molecules by utilizing vanadium-dependent haloperoxidase (VHPO) enzymology. This commentary will give perspective into our efforts to understand the unique VHPO-catalyzed conversions which modulate the activities within two ecologically relevant natural product families. Through enhancing our knowledge of microbial natural product biosynthesis, we can understand how and why these bioactive molecules are created.

El vanadio, desde su descubrimiento hasta su papel en la vida

<p>El vanadio es un elemento químico con una historia peculiar y tan fascinante como su química. Fue descubierto en el municipio argentífero de Zimapán, México, por Andrés Manuel Del Río, y redescubierto en Suecia por Nils Gabriel Sefström, quien lo nombró vanadio, en honor de la diosa nórdica <em>Vanadis</em>. El vanadio<em> </em>es el elemento número 22 más abundante en la corteza terrestre, y después del molibdeno, el segundo metal de transición con mayor presencia en disolución en el ambiente marino. Forma parte de más de 200 minerales entre los que se encuentra la vanadinita, Pb<sub>5</sub>(VO<sub>4</sub>)<sub>3</sub>Cl, y recientemente se encontró en su forma nativa en sublimados de fumarolas del cráter del volcán de Colima en México. El papel del vanadio en sistemas biológicos ha despertado el interés de la comunidad científica debido a varios hechos extraordinarios. Existen organismos exóticos que lo acumulan en cantidades excepcionales como las ascidias y los hongos alucinógenos del<em> </em>género<em> Amanita</em>. Además, se encuentra en la nitrogenasa de <em>Azobacter vinelandii</em> formando parte del cofactor FeVco, componente organometálico responsable de la “fijación” del nitrógeno atmosférico; también se presenta en las enzimas vanadio haloperoxidasas, las cuales intervienen indirectamente en el agotamiento del ozono atmosférico. A pesar de que la actividad antidiabetica del vanadio ha quedado bien establecida para sus estados de oxidación +4 y +5, actualmente no existe un medicamente basado en este metal para el tratamiento de la diabetes mellitus, enfermedad que actualmente padecen casi 13 millones de mexicanos.</p>

Vanadium-dependent haloperoxidase activity and phlorotannin incorporation into the cell wall during early embryogenesis of Fucus vesiculosus (Phaeophyceae)

ABSTRACT Vanadium-dependent haloperoxidases (V-HPO) are specific enzymes involved in the metabolism of reactive oxygen species in marine algae. These enzymes contribute to early embryogenesis of algae in the order Fucales, catalyzing the reactions which result in phlorotannin incorporation into the newly forming zygote cell wall and adhesive material. In this study we showed that early embryogenesis in Fucus vesiculosus is accompanied by synchronous changes of V-HPO activity, hydrogen peroxide content and content of cell-wall-associated phlorotannins. Phlorotannin incorporation into the cell wall of Fucus zygotes had already begun 1 h after fertilization, and this process was accompanied by rapid increase of H2O2 content and V-HPO activity. We suggest that altogether this initiates polymerization of phenolics and their cross-linking with the major cell wall constituent, alginic acid. Presumably, de novo phlorotannin biosynthesis is involved in this process, as GC-MS analysis showed dramatic changes in content of intracellular phloroglucinol and low-molecular-weight phlorotannins during the first 9 days of F. vesiculosus embryogenesis.

Chemoenzymatic Halocyclization of γ,δ-Unsaturated Carboxylic Acids and Alcohols.

Invited for this month's cover is the group of Prof. Dr. Frank Hollmann at Delft University of Technology in the Netherlands. The Front Cover shows the vanadium-dependent haloperoxidase from the marine organism Curcuvaria inaequalis, which efficiently activates halides as hypohalites that can then initiate spontaneous halo-lactonization and halo-etherification reactions. The Communication itself is available at 10.1002/cssc.201902240.

SelectedAspects of Iodate and Iodosalicylate Metabolism in Lettuce Including the Activity of Vanadium Dependent Haloperoxidases as Affected by Exogenous Vanadium

In marine algae, vanadium (V) regulates the cellular uptake of iodine (I) and its volatilization as I2, the processes catalyzed by vanadium-dependent haloperoxidases (vHPO). Relationships between I and vanadium V in higher plants, including crop plants, have not yet been described. Little is known about the possibility of the synthesis of plant-derived thyroid hormone analogs (PDTHA) in crop plants. The activity of vHPO in crop plants as well as the uptake and metabolism of iodosalicylates in lettuce have not yet been studied. This studyaimed to determine the effect of V on the uptake and accumulation of various forms of I, the metabolism of iodosalicylates and iodobenzoates and, finally, on the accumulation of T3 (triiodothyronine—as example of PDTHA) in plants. Lettuce (Lactuca sativa L. var. capitata ‘Melodion’ cv.) cultivation in a hydroponic NutrientFilm Technique (NFT) system was conducted with the introduction of 0 (control), 0.05, 0.1, 0.2, and 0.4 µM V doses of ammonium metavanadate (NH4VO3) in four independent experiments. No iodine treatment was applied in Experiment No. 1, while iodine compounds were applied at a dose of 10 µM (based on our own previous research) as KIO3, 5-iodosalicylic acid (5-ISA) and 3,5-diiodosalicylic acid (3,5-diISA) in Experiment Nos. 2, 3 and 4, respectively. When lettuce was grown at trace amount of I in the nutrient solution, increasing doses of V contributed to the increase of (a) I content in roots, (b) I uptake by whole lettuce plants (leaves + roots), and (c) vHPO activity in leaves (for doses 0.05–0.20 µM V). Vanadium was mainly found in roots where the content of this element increased proportionally to its dose. The content of V in leaves was not modified by V introduced into the nutrient solution. We found that5-ISA, 3,5-diISA and T3 were naturally synthesized in lettuce and its content increased when 5-ISA, 3,5-diISA were applied. Quantitative changes in the accumulation of organic metabolites (iodosalicylates and iodobenzoates) accumulation were observed, along with increased T3 synthesis, with its content in leaves exceeding the level of individual iodosalicylates and iodobenzoates. The content of T3 was not affected by V fertilization. It was concluded that iodosalicylates may participate in the biosynthesis pathway of T3—and probably of other PDTHA compounds.

Vanadium: Biological, Environmental, and Engineering Aspects

Vanadium is an element that is widely distributed in Earth’s crust as well as in sea-water and ground-water reservoirs. Therefore, it exerts a great influence on the issues related to life and environment. Vanadium is utilized by several marine organisms. For example, there are vanadate-dependent haloperoxidases in algae and several bacteria, e.g., Azotobacter, use it for nitrogen fixation and bacterial reduction involves the conversion of vanadate to oxidovanadium (IV). The similarity between vanadate and phosphate imparts a physiological functional role to vanadate (V), and consequently, several aspects of medicinal potential to vanadate and vanadium coordination compounds, such as their use in the treatment of diabetes, cancer, and cardiovascular problems, which may be explained in conjunction with vanadate/phosphate antagonism. Similar considerations apply to the efficacy of vanadium compounds in the treatment of HIV and [tropical] diseases caused by bacteria and protozoa. In addition to this biological efficacy, vanadium plays an increasingly recognized role in industrial processes, such as steel production, oxidation catalysis, and vanadium-based energy storage (batteries) and solar cells.

Effects of bromide-enriched natural seawater culture medium on protein and monoterpenes output of Ochtodes secundiramea (Rhodophyta, Gigartinales)

Benthic marine algae, especially Rhodophyta, are within a well-known marine group able to produce secondary metabolites with bioactive properties. Among them are halogenated terpenes, synthesized by vanadium-dependent haloperoxidase (V-BPO). The red alga Ochtodes secundiramea (Montagne) M. Howe produces high amounts of halogenated monoterpenes (HMT) which have the potential to control phytopathogenic fungi. Culture closed a system is a tool used to manipulate conditions to increase the synthesis of HMT and other metabolites. The apical segments of O. secundiramea were cultivated in a bioreactor, either in seawater enriched with half strength von Stosch’s solution (VSES/2) without (control) and with the addition of 250 mg L−1 bromine (treatment). In response to these conditions, specific growth rate, HMT profile, soluble protein, phycobiliproteins, soluble carbohydrate, and chlorophyll as well as the V-BPO activity, uptake, and accumulated bromine within the biomass were evaluated. The treatment did not promote significant alterations in the growth but increased the V-BPO activity and bromine uptake and incorporation (2.5 fold). No changes in the HMT profiles of the extracts from both cultures conditions were observed by gas chromatography–mass spectrometry analyses, whereas the values of total soluble protein and phycobiliproteins were 2-fold higher in samples from the bromine-enriched medium when compared to samples from control. These results support the evidences of protective effects promoted by V-BPO activity. Furthermore, carbohydrate and chlorophyll contents were not affected by experimental conditions. These results provided new low-cost strategies that can be applied to increase of certain biomass components, which here are algal proteins, especially in Rhodophyta-based biotechnological industries for food and agriculture.

Bromination of alkyl quinolones by Microbulbifer sp. HZ11, a marine Gammaproteobacterium, modulates their antibacterial activity.

Alkyl quinolones (AQs) are multifunctional bacterial secondary metabolites generally known for their antibacterial and algicidal properties. Certain representatives are also employed as signalling molecules of Burkholderia strains and Pseudomonas aeruginosa. The marine Gammaproteobacterium Microbulbifer sp. HZ11 harbours an AQ biosynthetic gene cluster with unusual topology but does not produce any AQ-type metabolites under laboratory conditions. In this study, we demonstrate the potential of strain HZ11 for AQ production by analysing intermediates and key enzymes of the pathway. Moreover, we demonstrate that exogenously added AQs such as 2-heptyl-1(H)-quinolin-4-one (referred to as HHQ) or 2-heptyl-1-hydroxyquinolin-4-one (referred to as HQNO) are brominated by a vanadium-dependent haloperoxidase (V-HPOHZ11 ), which preferably is active towards AQs with C5-C9 alkyl side chains. Bromination was specific for the third position and led to 3-bromo-2-heptyl-1(H)-quinolin-4-one (BrHHQ) and 3-bromo-2-heptyl-1-hydroxyquinolin-4-one (BrHQNO), both of which were less toxic for strain HZ11 than the respective parental compounds. In contrast, BrHQNO showed increased antibiotic activity against Staphylococcus aureus and marine isolates. Therefore, bromination of AQs by V-HPOHZ11 can have divergent consequences, eliciting a detoxifying effect for strain HZ11 while simultaneously enhancing antibiotic activity against other bacteria.