315 research outputs found
Lipoxygenases - Structure and reaction mechanism
No full textLipid oxidation is a common metabolic reaction in all biological systems, appearing in developmentally regulated processes and as response to abiotic and biotic stresses. Products derived from lipid oxidation processes are collectively named oxylipins. Initial lipid oxidation may either occur by chemical reactions or is derived from the action of enzymes. In plants this reaction is mainly catalyzed by lipoxygenase (LOXs) enzymes and during recent years analysis of different plant LOXs revealed insights into their enzyme mechanism. This review aims at giving an overview of concepts explaining the catalytic mechanism of LOXs as well as the different regio- and stereo-specificities of these enzymes. (c) 2009 Elsevier Ltd. All rights reserved
Biosynthesis of oxylipins in non-mammals
No full textLipid peroxidation is common to all biological systems, appearing in developmentally-regulated processes and as a response to environmental changes. Products derived from lipid peroxidation are collectively named oxylipins. Initial lipid peroxidation may either occur by enzymatic or chemical reactions. An array of alternative reactions further converting lipid hydroperoxides gives rise to a large variety of oxylipin classes, some with reported signaling functions in plants, fungi, algae or animals. The structural diversity of oxylipins is further increased by their occurrence either as esters in complex lipids or as free (non-esterified) fatty acid derivatives. The enzymes involved in oxylipin metabolism are diverse and comprise a multitude of examples with interesting and unusual catalytic properties. This review aims at giving an overview on plant, fungal, algal and bacterial oxylipins and the enzymes responsible for their biosynthesis. (C) 2009 Elsevier Ltd. All rights reserved
A Bisallylic Mini-lipoxygenase from Cyanobacterium Cyanothece sp That Has an Iron as Cofactor
No full textLipoxygenases are enzymes that are found ubiquitously in higher animals and plants, but have only recently been identified in a number of bacteria. The genome of the diazotrophic unicellular cyanobacterium Cyanothece sp. harbors two genes with homology to lipoxygenases. Here we describe the isolation of one gene, formerly named csplox2. It was cloned, and the protein was expressed in Escherichia coli and purified. The purified enzyme belongs to the group of prokaryotic mini lipoxygenases, because it had a molecular mass of 65 kDa. Interestingly, it catalyzed the conversion of linoleic acid, the only endogenously found polyunsaturated fatty acid, primarily to the bisallylic hydroperoxide 11R-hydroperoxyoctadecadienoic acid. This product had previously only been described for the manganese lipoxygenase from the take all fungus, Gaeumannomyces graminis. By contrast, CspLOX2 was shown to be an iron lipoxygenase. In addition, CspLOX2 formed a mixture of typical conjugated lipoxygenase products, e. g. 9R- and 13S-hydroperoxide. The conversion of linoleic acid took place with a maximum reaction rate of 31 s(-1). Incubation of the enzyme with [(11S)-(2)H] linoleic acid led to the formation of hydroperoxides that had lost the deuterium label, thus suggesting that CspLOX2 catalyzes antarafacial oxygenation as opposed to the mechanism of manganese lipoxygenase. CspLOX2 could also oxidize diarachidonylglycerophosphatidylcholine with similar specificity as the free fatty acid, indicating that binding of the substrate takes place with a "tail-first" orientation. We conclude that CspLOX2 is a novel iron mini-lipoxygenase that catalyzes the formation of bisallylic hydroperoxide as the major product
Properties of a mini 9R-lipoxygenase from Nostoc sp. PCC 7120 and its mutant forms
No full textLipoxygenases (LOXs) consist of a class of enzymes that catalyze the regio- and stereospecific dioxygenation of polyunsaturated fatty acids. Current reports propose that a conserved glycine residue in the active site of R-lipoxygenases and an alanine residue at the corresponding position in S-lipoxygenases play a crucial role in determining the stereochemistry of the product. Recently, a bifunctional lipoxygenase with a linoleate diol synthase activity from Nostoc sp. PCC7120 with R stereospecificity and the so far unique feature of carrying an alanine instead of the conserved glycine in the position of the sequence determinant for chiral specificity was identified. The recombinant carboxy-terminal domain was purified after expression in E. coli. The ability of the enzyme to use linoleic acid esterified to a bulky phosphatidylcholine molecule as a substrate suggested a tail-fist binding orientation of the substrate. Site directed mutagenesis of the alanine to glycine did not cause alterations in the stereospecificity of the products, while mutation of the alanine to valine or isoleucine modified both regio- and enantioselectivity of the enzyme. Kinetic measurements revealed that substitution of Ala by Gly or Val did not significantly influence the reaction characteristics, while the A162I mutant showed a reduced vmax. Based on the mutagenesis data obtained, we suggest that the existing model for stereocontrol of the lipoxygenase reaction may be expanded to include enzymes that seem to have in general a smaller amino acid in R and a bulkier one in S lipoxygenases at the position that controls stereospecificity
On the Substrate Binding of Linoleate 9‐Lipoxygenases
No full textLipoxygenases (LOX; linoleate:oxygen oxidoreductase EC 1.13.11.12) consist of a class of enzymes that catalyze the regio- and stereo specific dioxygenation of polyunsaturated fatty acids. Here we characterize two proteins that belong to the less studied class of 9-LOXs, Solanum tuberosum StLOX1 and Arabidopsis thaliana AtLOX1. The proteins were recombinantly expressed in E. coli and the product specificity of the enzymes was tested against different fatty acid substrates. Both enzymes showed high specificity against all tested C18 fatty acids and produced (9S)-hydroperoxides. However, incubation of the C20 fatty acid arachidonic acid with AtLOX1 gave a mixture of racemic hydroperoxides. On the other hand, with StLOX1 we observed the formation of a mixture of products among which the (5S)-hydroperoxy eicosatetraenoic acid (5S-H(P)ETE) was the most abundant. Esterified fatty acids were no substrates. We used site directed mutagenesis to modify a conserved valine residue in the active site of StLOX1 and examine the importance of space within the active site, which has been shown to play a role in determining the positional specificity. The Val576Phe mutant still catalyzed the formation of (9S)-hydroperoxides with C18 fatty acids, while it exhibited altered specificity against arachidonic acid and produced mainly (11S)-H(P)ETE. These data confirm the model that in case of linoleate 9-LOX binding of the substrate takes place with the carboxyl-group first
Crystal structure of a lipoxygenase from Cyanothece sp may reveal novel features for substrate acquisition
No full textIn eukaryotes, oxidized PUFAs, so-called oxylipins, are vital signaling molecules. The first step in their biosynthesis may be catalyzed by a lipoxygenase (LOX), which forms hydroperoxides by introducing dioxygen into PUFAs. Here we characterized CspLOX1, a phylogenetically distant LOX family member from Cyanothece sp. PCC 8801 and determined its crystal structure. In addition to the classical two domains found in plant, animal, and coral LOXs, we identified an N-terminal helical extension, reminiscent of the long alpha-helical insertion in Pseudomonas aeruginosa LOX. In liposome flotation studies, this helical extension, rather than the beta-barrel domain, was crucial for a membrane binding function. Additionally, CspLOX1 could oxygenate 1,2-diarachidonyl-sn-glycero-3-phosphocholine, suggesting that the enzyme may act directly on membranes and that fatty acids bind to the active site in a tail-first orientation. This binding mode is further supported by the fact that CspLOX1 catalyzed oxygenation at the n-10 position of both linoleic and arachidonic acid, resulting in 9R- and 11R-hydroperoxides, respectively. Together these results reveal unifying structural features of LOXs and their function. While the core of the active site is important for lipoxygenation and thus highly conserved, peripheral domains functioning in membrane and substrate binding are more variable
A multimodal-corpus data collection system for cognitive acoustic scene analysis
No full textWe report on the design and the collection of a multi-modal data corpus for cognitive acoustic scene analysis. Sounds are generated by stationary and moving sources (people), that is by omni-directional speakers mounted on people's heads. One or two subjects walk along predetermined systematic and random paths, in synchrony and out of sync. Sound is captured in multiple microphone systems, including a four MEMS microphone directional array, two electret microphones situated in the ears of a stuffed gerbil head, and a Head Acoustics, head-shoulder unit with ICP microphones. Three micro-Doppler units operating at different frequencies were employed to capture gait and the articulatory signatures as well as location of the people in the scene. Three ground vibration sensors were recording the footsteps of the walking people. A 3D MESA camera as well as a web-cam provided 2D and 3D visual data for system calibration and ground truth. Data were collected in three environments ranging from a well controlled environment (anechoic chamber), an indoor environment (large classroom) and the natural environment of an outside courtyard. A software tool has been developed for the browsing and visualization of the data.Fil: Georgiou, Juliu. University of Cyprus; ChipreFil: Philippe, Pouliquen. University Johns Hopkins; Estados Unidos. University of Cyprus; ChipreFil: Cassidy, Andrew. University Johns Hopkins; Estados Unidos. University of Cyprus; ChipreFil: Garreau, Guillaume. University of Cyprus; ChipreFil: Charalambos, Andreou. University of Cyprus; ChipreFil: Stuarts, Guillermo Héctor. University of Cyprus; Chipre. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: d'Urbal, Cirille. University of Cyprus; ChipreFil: Andreou, Andreas. University of Cyprus; Chipre. University Johns Hopkins; Estados UnidosFil: Denham, Susan. University of Plymouth; Reino UnidoFil: Wennekers, Thomas. University of Plymouth; Reino UnidoFil: Mill, Robert. University of Plymouth; Reino UnidoFil: Winkler, Istvan. Hungarian Academy of Sciences; HungríaFil: Bohm, Tamas. Hungarian Academy of Sciences; HungríaFil: Szalardy, Orsolya. Hungarian Academy of Sciences; HungríaFil: Klump, George. University of Oldenburg; AlemaniaFil: Jones, Simon. University of Oldenburg; AlemaniaFil: Bendixen, Alexandra. Universitat Leipzig; AlemaniaInformation Sciences and Systems (CISS), 2011 45th Annual Conference onBaltimoreEstados UnidosInstitute of Electrical and Electronics Engineer
The relationship between personality, normative behavior and fear of COVID-19
No full textSyftet med föreliggande studie var att undersöka sambandet mellan personlighet och normativt beteende, i denna studie definierat som hygienbeteende i följandet av rekommendationer för COVID-19. Studien undersökte även sambandet mellan personlighet och rädsla för COVID-19, samt könsskillnader i hygienbeteende och rädsla för COVID-19. Studiematerialet utgjordes av svaren från en enkät (N = 160). Enkäten mätte personlighet utifrån NEO-FFI-3 och rädsla för COVID-19 (FCV-19S), samt följandet av rekommendationer för COVID-19 (hygienbeteende). Resultaten visade att hög grad av målmedvetenhet korrelerade positivt till att följa rekommendationerna och att hög grad av känslomässig instabilitet och vänlighet korrelerade positivt med rädsla för COVID-19. Studien fann även att kvinnor rapporterade högre i rädsla för COVID-19, samt en högre anpassning i beteende för att följa rekommendationerna. Resultaten går i linje med tidigare forskning, men framtida forskning bör vidare undersöka sambandet mellan personlighet och rädsla för COVID-19, samt om det kan finnas kulturella skillnader.The aim of the study was to examine the relationship between personality and normative behavior, defined as compliance to recommendations, and the relationship between personality and fear of COVID-19. The study also examined gender differences in compliance to recommendations and fear of COVID-19. The sample consisted of Swedish university students (N = 160). Questionnaires were used to collect data, and it measured personality (NEO-FFI-3), fear of COVID-19 (FCV-19S) and compliance to recommendations. The results showed that individuals with high scores on conscientiousness were more likely to comply with the recommendations. High scores on neuroticism and agreeableness were positive correlated with high fear for COVID-19. Women reported higher fear for COVID-19 and were more likely to comply with the recommendations. These results are in line with previous research, but future research need to investigate the relationship between personality and fear of COVID-19 and if there are any cultural differences
CORRECTION: Tracking repeat spawning anadromous fish migrations over multiple years in a fragmented river suggests philopatry and sex-linked variation in space use
No full textThe article “Tracking repeat spawning anadromous fsh migrations over multiple years in a fragmented river suggests philopatry and sex-linked variation in space use”, written by Peter Davies, J. Robert Britton, Demetra Andreou, Charles Crundwell, Jamie R. Dodd, Olivier Lepais, Andrew D. Nunn, Stephen Sabatino, Randolph Velterop, Jonathan D. Bolland was originally published under © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024. As a result of the subsequent decision to publish the article under the open access model, the article’s copyright notice was changed on 19 February 2025 to © The Author(s) 2025 and the article is now distributed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0
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