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Liu J, Li X, Zhu Q, Zhou J, Shi L, Lu W, Bao L, Meng L, Wu L, Zhang N, Christie P. Differences in the activities of six soil enzymes in response to cadmium contamination of paddy soils in high geological background areas. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 346:123704. [PMID: 38442823 DOI: 10.1016/j.envpol.2024.123704] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 02/29/2024] [Accepted: 03/01/2024] [Indexed: 03/07/2024]
Abstract
East Yunnan province in southwest China is a region with elevated natural abundance (high geological background levels) of Cd due to high metal (loid) contents in the soils. Enzyme activities are useful indicators of metal (loid) toxicity in contaminated soils and whether Cd inhibits enzyme activities in paddy soils in high geological background areas is of considerable public concern. A pot experiment combined with field investigation was conducted to assess the effects of Cd on six soil enzymes that are essential to the cycling of C, N, and P in soils. Inhibitory effects of Cd fractions on enzyme activities were assessed using ecological dose-response models. The impact of soil properties on the inhibition of sensitive soil enzymes by Cd were assessed using linear and structural equation models. Cadmium was enriched in the paddy soils with 72.2 % of soil samples from high geological background areas exceeding the Chinese threshold values (GB 15618-2018) of Cd. Enzyme responses to Cd contamination varied markedly with a negative response by catalase but a positive response by invertase. Urease, β-glucosidase, and alkaline phosphatase activities were stimulated at low Cd concentrations and inhibited at high concentrations. The average inhibition ratios of β-glucosidase, urease, and catalase in high Cd levels were 19.9, 38.9, and 51.9%, respectively. Ecological dose-response models indicate that catalase and urease were the most Cd-sensitive of the enzymes studied and were suitable indicators of soil quality in high geological background areas. Structural equation modeling (SEM) indicates that soil properties influenced sensitive enzymes through various pathways, indicating that soil properties were factors determining Cd inhibition of enzyme activities. This suggests that Cd concentrations and soil physicochemical properties under a range of environmental conditions should be considered in addressing soil Cd pollution.
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Affiliation(s)
- Juan Liu
- College of Resources and Environmental Science, Yunnan Agricultural University, Kunming 650201, China; State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
| | - Xinyang Li
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
| | - Qilin Zhu
- College of Tropical Crops, Hainan University, Haikou 570228, China.
| | - Jiawen Zhou
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
| | - Lingfeng Shi
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
| | - Weihong Lu
- Yunnan Soil Fertility and Pollution Restoration Laboratory, Yunnan Agricultural University, Kunming 650201, China; School of Environment and Surveying Engineering, Suzhou University, Suzhou 234099, China.
| | - Li Bao
- College of Resources and Environmental Science, Yunnan Agricultural University, Kunming 650201, China; Yunnan Soil Fertility and Pollution Restoration Laboratory, Yunnan Agricultural University, Kunming 650201, China.
| | - Lei Meng
- College of Tropical Crops, Hainan University, Haikou 570228, China.
| | - Longhua Wu
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
| | - Naiming Zhang
- College of Resources and Environmental Science, Yunnan Agricultural University, Kunming 650201, China; Yunnan Soil Fertility and Pollution Restoration Laboratory, Yunnan Agricultural University, Kunming 650201, China.
| | - Peter Christie
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China.
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Zonnequin M, Belcour A, Delage L, Siegel A, Blanquart S, Leblanc C, Markov GV. Empirical evidence for metabolic drift in plant and algal lipid biosynthesis pathways. FRONTIERS IN PLANT SCIENCE 2024; 15:1339132. [PMID: 38357267 PMCID: PMC10864609 DOI: 10.3389/fpls.2024.1339132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 01/15/2024] [Indexed: 02/16/2024]
Abstract
Metabolic pathway drift has been formulated as a general principle to help in the interpretation of comparative analyses between biosynthesis pathways. Indeed, such analyses often indicate substantial differences, even in widespread pathways that are sometimes believed to be conserved. Here, our purpose is to check how much this interpretation fits to empirical data gathered in the field of plant and algal biosynthesis pathways. After examining several examples representative of the diversity of lipid biosynthesis pathways, we explain why it is important to compare closely related species to gain a better understanding of this phenomenon. Furthermore, this comparative approach brings us to the question of how much biotic interactions are responsible for shaping this metabolic plasticity. We end up introducing some model systems that may be promising for further exploration of this question.
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Affiliation(s)
- Maëlle Zonnequin
- Sorbonne Université, CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Roscoff, France
| | - Arnaud Belcour
- Univ Rennes, Inria, CNRS, IRISA, Equipe Dyliss, Rennes, France
- Univ. Grenoble Alpes, Inria, Grenoble, France
| | - Ludovic Delage
- Sorbonne Université, CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Roscoff, France
| | - Anne Siegel
- Univ Rennes, Inria, CNRS, IRISA, Equipe Dyliss, Rennes, France
| | | | - Catherine Leblanc
- Sorbonne Université, CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Roscoff, France
| | - Gabriel V. Markov
- Sorbonne Université, CNRS, Integrative Biology of Marine Models (LBI2M, UMR8227), Station Biologique de Roscoff (SBR), Roscoff, France
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Toporkova YY, Smirnova EO, Gorina SS. Epoxyalcohol Synthase Branch of Lipoxygenase Cascade. Curr Issues Mol Biol 2024; 46:821-841. [PMID: 38248355 PMCID: PMC10813956 DOI: 10.3390/cimb46010053] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2023] [Revised: 01/12/2024] [Accepted: 01/15/2024] [Indexed: 01/23/2024] Open
Abstract
Oxylipins are one of the most important classes of bioregulators, biosynthesized through the oxidative metabolism of unsaturated fatty acids in various aerobic organisms. Oxylipins are bioregulators that maintain homeostasis at the cellular and organismal levels. The most important oxylipins are mammalian eicosanoids and plant octadecanoids. In plants, the main source of oxylipins is the lipoxygenase cascade, the key enzymes of which are nonclassical cytochromes P450 of the CYP74 family, namely allene oxide synthases (AOSs), hydroperoxide lyases (HPLs), and divinyl ether synthases (DESs). The most well-studied plant oxylipins are jasmonates (AOS products) and traumatin and green leaf volatiles (HPL products), whereas other oxylipins remain outside of the focus of researchers' attention. Among them, there is a large group of epoxy hydroxy fatty acids (epoxyalcohols), whose biosynthesis has remained unclear for a long time. In 2008, the first epoxyalcohol synthase of lancelet Branchiostoma floridae, BfEAS (CYP440A1), was discovered. The present review collects data on EASs discovered after BfEAS and enzymes exhibiting EAS activity along with other catalytic activities. This review also presents the results of a study on the evolutionary processes possibly occurring within the P450 superfamily as a whole.
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Affiliation(s)
- Yana Y. Toporkova
- Kazan Institute of Biochemistry and Biophysics, FRC Kazan Scientific Center of RAS, P.O. Box 261, 420111 Kazan, Russia; (E.O.S.); (S.S.G.)
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Somasundaram S, Abraham JS, Maurya S, Toteja R, Gupta R, Makhija S. Molecular characterization and transcriptional modulation of stress-responsive genes under heavy metal stress in freshwater ciliate, Euplotes aediculatus. ECOTOXICOLOGY (LONDON, ENGLAND) 2022; 31:271-288. [PMID: 34982303 DOI: 10.1007/s10646-021-02518-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 12/24/2021] [Indexed: 06/14/2023]
Abstract
Heavy metal pollutants in the environment are increasing exponentially due to various anthropogenic factors including mining, industrial and agricultural wastes. Living organisms exposed to heavy metals above a certain threshold level induces deleterious effects in these organisms. To live in such severe environments, microbes have developed a range of tolerance mechanisms which include upregulation of stress-responsive genes and/or antioxidant enzymes to detoxify the metal stress. Single cell eukaryotic microorganisms, i.e., ciliates, are highly sensitive to environmental pollutants mainly due to the absence of cell wall, which make them suitable candidates for conducting ecotoxicological studies. Therefore, the present investigation describes the effects of heavy metals (cadmium and copper) on freshwater ciliate, Euplotes aediculatus. The activities of antioxidant enzymes, i.e., catalase and glutathione peroxidase in E. aediculatus were determined under heavy metal exposure. Besides, the expression of stress-responsive genes, namely, heat-shock protein 70 (hsp70) and catalase (cat), has also been determined in this freshwater ciliate species under metal stress. The present study showed that the enzyme activity and the expression of these genes increased with an increase in the heavy metal concentration and with the duration of metal exposure. Also, these stress-responsive genes were sequenced and characterized to comprehend their role in cell rescue.
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Affiliation(s)
- Sripoorna Somasundaram
- Ciliate Biology Laboratory, Acharya Narendra Dev College, University of Delhi, Delhi, India
| | - Jeeva Susan Abraham
- Ciliate Biology Laboratory, Acharya Narendra Dev College, University of Delhi, Delhi, India
| | - Swati Maurya
- Ciliate Biology Laboratory, Acharya Narendra Dev College, University of Delhi, Delhi, India
| | - Ravi Toteja
- Ciliate Biology Laboratory, Acharya Narendra Dev College, University of Delhi, Delhi, India
| | - Renu Gupta
- Zoology Department, Maitreyi College, University of Delhi, Delhi, India
| | - Seema Makhija
- Ciliate Biology Laboratory, Acharya Narendra Dev College, University of Delhi, Delhi, India.
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Detection of the First Epoxyalcohol Synthase/Allene Oxide Synthase (CYP74 Clan) in the Lancelet ( Branchiostoma belcheri, Chordata). Int J Mol Sci 2021; 22:ijms22094737. [PMID: 33947016 PMCID: PMC8124189 DOI: 10.3390/ijms22094737] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2021] [Revised: 04/27/2021] [Accepted: 04/27/2021] [Indexed: 12/04/2022] Open
Abstract
The CYP74 clan cytochromes (P450) are key enzymes of oxidative metabolism of polyunsaturated fatty acids in plants, some Proteobacteria, brown and green algae, and Metazoa. The CYP74 enzymes, including the allene oxide synthases (AOSs), hydroperoxide lyases, divinyl ether synthases, and epoxyalcohol synthases (EASs) transform the fatty acid hydroperoxides to bioactive oxylipins. A novel CYP74 clan enzyme CYP440A18 of the Asian (Belcher’s) lancelet (Branchiostoma belcheri, Chordata) was biochemically characterized in the present work. The recombinant CYP440A18 enzyme was active towards all substrates used: linoleate and α-linolenate 9- and 13-hydroperoxides, as well as with eicosatetraenoate and eicosapentaenoate 15-hydroperoxides. The enzyme specifically converted α-linolenate 13-hydroperoxide (13-HPOT) to the oxiranyl carbinol (9Z,11R,12R,13S,15Z)-11-hydroxy-12,13-epoxy-9,15-octadecadienoic acid (EAS product), α-ketol, 12-oxo-13-hydroxy-9,15-octadecadienoic acid (AOS product), and cis-12-oxo-10,15-phytodienoic acid (AOS product) at a ratio of around 35:5:1. Other hydroperoxides were converted by this enzyme to the analogous products. In contrast to other substrates, the 13-HPOT and 15-HPEPE yielded higher proportions of α-ketols, as well as the small amounts of cyclopentenones, cis-12-oxo-10,15-phytodienoic acid and its higher homologue, dihomo-cis-12-oxo-3,6,10,15-phytotetraenoic acid, respectively. Thus, the CYP440A18 enzyme exhibited dual EAS/AOS activity. The obtained results allowed us to ascribe a name “B. belcheri EAS/AOS” (BbEAS/AOS) to this enzyme. BbEAS/AOS is a first CYP74 clan enzyme of Chordata species possessing AOS activity.
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Catalase-Related Allene Oxide Synthase, on a Biosynthetic Route to Fatty Acid Cyclopentenones: Expression and Assay of the Enzyme and Preparation of the 8R-HPETE Substrate. Methods Enzymol 2018. [PMID: 29909837 DOI: 10.1016/bs.mie.2018.02.019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
Catalase-related allene oxide synthase (cAOS) is a hemoprotein that converts a specific fatty acid hydroperoxide to an unstable allene oxide intermediate at turnover rates in the order of 1000 per second. Fatty acid allene oxides are intermediates in the formation of cyclopentenone or hydrolytic products in marine systems, most notably the prostanoid-related clavulones. Although the key catalytic amino acid residues around the active site of cAOS are the same as in true catalases, cAOS does not react with hydrogen peroxide. cAOS occurs exclusively as the N-terminal domain of a naturally occurring fusion protein with a C-terminal lipoxygenase (LOX) domain that supplies the hydroperoxide substrate. In marine invertebrates, an 8R-LOX domain converts arachidonic acid to 8R-hydroperoxyeicosatetraenoic acid (8R-HPETE) and the cAOS domain forms an 8,9-epoxy allene oxide. The fusion protein from the sea whip octocoral Plexaura homomalla is the prototypical model with crystal structures of the individual domains. The cAOS (43kDa) expresses exceptionally well in Escherichia coli, with yields of up to 100mg/L. This article describes in detail expression and assay of the P. homomalla cAOS and two methods for the preparation of its 8R-HPETE substrate. Another article in this volume focuses on the P. homomalla 8R-LOX (Gilbert, Neau, & Newcomer, 2018).
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Huang X, Groves JT. Oxygen Activation and Radical Transformations in Heme Proteins and Metalloporphyrins. Chem Rev 2018; 118:2491-2553. [PMID: 29286645 PMCID: PMC5855008 DOI: 10.1021/acs.chemrev.7b00373] [Citation(s) in RCA: 579] [Impact Index Per Article: 96.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Indexed: 12/20/2022]
Abstract
As a result of the adaptation of life to an aerobic environment, nature has evolved a panoply of metalloproteins for oxidative metabolism and protection against reactive oxygen species. Despite the diverse structures and functions of these proteins, they share common mechanistic grounds. An open-shell transition metal like iron or copper is employed to interact with O2 and its derived intermediates such as hydrogen peroxide to afford a variety of metal-oxygen intermediates. These reactive intermediates, including metal-superoxo, -(hydro)peroxo, and high-valent metal-oxo species, are the basis for the various biological functions of O2-utilizing metalloproteins. Collectively, these processes are called oxygen activation. Much of our understanding of the reactivity of these reactive intermediates has come from the study of heme-containing proteins and related metalloporphyrin compounds. These studies not only have deepened our understanding of various functions of heme proteins, such as O2 storage and transport, degradation of reactive oxygen species, redox signaling, and biological oxygenation, etc., but also have driven the development of bioinorganic chemistry and biomimetic catalysis. In this review, we survey the range of O2 activation processes mediated by heme proteins and model compounds with a focus on recent progress in the characterization and reactivity of important iron-oxygen intermediates. Representative reactions initiated by these reactive intermediates as well as some context from prior decades will also be presented. We will discuss the fundamental mechanistic features of these transformations and delineate the underlying structural and electronic factors that contribute to the spectrum of reactivities that has been observed in nature as well as those that have been invented using these paradigms. Given the recent developments in biocatalysis for non-natural chemistries and the renaissance of radical chemistry in organic synthesis, we envision that new enzymatic and synthetic transformations will emerge based on the radical processes mediated by metalloproteins and their synthetic analogs.
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Affiliation(s)
- Xiongyi Huang
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
- Department
of Chemistry, California Institute of Technology, Pasadena, California 91125, United States
| | - John T. Groves
- Department
of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
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Toporkova YY, Gorina SS, Mukhitova FK, Hamberg M, Ilyina TM, Mukhtarova LS, Grechkin AN. Identification of CYP443D1 (CYP74 clan) of Nematostella vectensis as a first cnidarian epoxyalcohol synthase and insights into its catalytic mechanism. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:1099-1109. [PMID: 28774820 DOI: 10.1016/j.bbalip.2017.07.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2017] [Revised: 06/16/2017] [Accepted: 07/29/2017] [Indexed: 01/08/2023]
Abstract
The CYP74 clan enzymes are responsible for the biosynthesis of numerous bioactive oxylipins in higher plants, some Proteobacteria, brown and green algae, and Metazoa. A novel putative CYP74 clan gene CYP443D1 of the starlet sea anemone (Nematostella vectensis, Cnidaria) has been cloned, and the properties of the corresponding recombinant protein have been studied in the present work. The recombinant CYP443D1 was incubated with the 9- and 13-hydroperoxides of linoleic and α-linolenic acids (9-HPOD, 13-HPOD, 9-HPOT, and 13-HPOT, respectively), as well as with the 9-hydroperoxide of γ-linolenic acid (γ-9-HPOT) and 15-hydroperoxide of eicosapentaenoic acid (15-HPEPE). The enzyme was active towards all C18-hydroperoxides with some preference to 9-HPOD. In contrast, 15-HPEPE was a poor substrate. The CYP443D1 specifically converted 9-HPOD into the oxiranyl carbinol 1, (9S,10R,11S,12Z)-9,10-epoxy-11-hydroxy-12-octadecenoic acid. Both 18O atoms from [18O2-hydroperoxy]9-HPOD were virtually quantitatively incorporated into product 1. Thus, the CYP443D1 exhibited epoxyalcohol synthase (EAS) activity. The 18O labelling data demonstrated that the reaction mechanism included three sequential steps: (1) hydroperoxyl homolysis, (2) oxy radical rearrangement into epoxyallylic radical, (3) hydroxyl rebound, resulting in oxiranyl carbinol formation. The 9-HPOT and γ-9-HPOT were also specifically converted into the oxiranyl carbinols, 15,16- and 6,7-dehydro analogues of compound 1, respectively. The 13-HPOD was converted into erythro- and threo-isomers of oxiranyl carbinol, as well as oxiranyl vinyl carbinols. The obtained results allow assignment of the name "N. vectensis EAS" (NvEAS) to CYP443D1. The NvEAS is a first EAS detected in Cnidaria.
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Affiliation(s)
- Yana Y Toporkova
- Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan 420111, Russia
| | - Svetlana S Gorina
- Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan 420111, Russia
| | - Fakhima K Mukhitova
- Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan 420111, Russia
| | - Mats Hamberg
- Division of Physiological Chemistry II, Department of Medical Biochemistry and Biophysics, Karolinska Institutet, S-17177 Stockholm, Sweden
| | - Tatyana M Ilyina
- Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan 420111, Russia
| | - Lucia S Mukhtarova
- Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan 420111, Russia
| | - Alexander N Grechkin
- Kazan Institute of Biochemistry and Biophysics, Russian Academy of Sciences, P.O. Box 30, Kazan 420111, Russia.
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Oxidation of C18 Hydroxy-Polyunsaturated Fatty Acids to Epoxide or Ketone by Catalase-Related Hemoproteins Activated with Iodosylbenzene. Lipids 2017. [PMID: 28631071 DOI: 10.1007/s11745-017-4271-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Small catalase-related hemoproteins with a facility to react with fatty acid hydroperoxides were examined for their potential mono-oxygenase activity when activated using iodosylbenzene. The proteins tested were a Fusarium graminearum 41 kD catalase hemoprotein (Fg-cat, gene FGSG_02217), a Pseudomonas fluorescens Pfl01 catalase (37.5 kD, accession number WP_011333788.1), and a Mycobacterium avium ssp. paratuberculosis 33 kD catalase (gene MAP-2744c). 13-Hydroxy-octadecenoic acids (which are normally unreactive) were selected as substrates because these enzymes react specifically with the corresponding 13S-hydroperoxides (Pakhomova et al. 18:2559-2568, 5; Teder et al. 1862:706-715, 14). In the presence of iodosylbenzene Fg-cat converted 13S-hydroxy-fatty acids to two products: the 15,16-double bond of 13S-hydroxy α-linolenic acid was oxidized stereospecifically to the 15S,16R-cis-epoxide or the 13-hydroxyl was oxidized to the 13-ketone. Products were identified by UV, HPLC, LC-MS, NMR and by comparison with authentic standards prepared for this study. The Pfl01-cat displayed similar activity. MAP-2744c oxidized 13S-hydroxy-linoleic acid to the 13-ketone, and epoxidized the double bonds to form the 9,10-epoxy-13-hydroxy, 11,12-epoxy-13-hydroxy, and 9,10-epoxy-13-keto derivatives; equivalent transformations occurred with 9S-hydroxy-linoleic acid as substrate. In parallel incubations in the presence of iodosylbenzene, human catalase displayed no activity towards 13S-hydroxy-linoleic acid, as expected from the highly restricted access to its active site. The results indicated that with suitable transformation to Compound I, monooxygenase activity can be demonstrated by these catalase-related hemoproteins with tyrosine as the proximal heme ligand.
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Teder T, Boeglin WE, Schneider C, Brash AR. A fungal catalase reacts selectively with the 13S fatty acid hydroperoxide products of the adjacent lipoxygenase gene and exhibits 13S-hydroperoxide-dependent peroxidase activity. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:706-715. [PMID: 28363790 DOI: 10.1016/j.bbalip.2017.03.011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2016] [Revised: 03/08/2017] [Accepted: 03/27/2017] [Indexed: 11/16/2022]
Abstract
The genome of the fungal plant pathogen Fusarium graminearum harbors six catalases, one of which has the sequence characteristics of a fatty acid peroxide-metabolizing catalase. We cloned and expressed this hemoprotein (designated as Fg-cat) along with its immediate neighbor, a 13S-lipoxygenase (cf. Brodhun et al., PloS One, e64919, 2013) that we considered might supply a fatty acid hydroperoxide substrate. Indeed, Fg-cat reacts abruptly with the 13S-hydroperoxide of linoleic acid (13S-HPODE) with an initial rate of 700-1300s-1. By comparison there was no reaction with 9R- or 9S-HPODEs and extremely weak reaction with 13R-HPODE (~0.5% of the rate with 13S-HPODE). Although we considered Fg-cat as a candidate for the allene oxide synthase of the jasmonate pathway in fungi, the main product formed from 13S-HPODE was identified by UV, MS, and NMR as 9-oxo-10E-12,13-cis-epoxy-octadecenoic acid (with no traces of AOS activity). The corresponding analog is formed from the 13S-hydroperoxide of α-linolenic acid along with novel diepoxy-ketones and two C13 aldehyde derivatives, the reaction mechanisms of which are proposed. In a peroxidase assay monitoring the oxidation of ABTS, Fg-cat exhibited robust activity (kcat 550s-1) using the 13S-hydroperoxy-C18 fatty acids as the oxidizing co-substrate. There was no detectable peroxidase activity using the corresponding 9S-hydroperoxides, nor with t-butyl hydroperoxide, and very weak activity with H2O2 or cumene hydroperoxide at micromolar concentrations of Fg-cat. Fg-cat and the associated lipoxygenase gene are present together in fungal genera Fusarium, Metarhizium and Fonsecaea and appear to constitute a partnership for oxidations in fungal metabolism or defense.
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Affiliation(s)
- Tarvi Teder
- Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
| | - William E Boeglin
- Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
| | - Claus Schneider
- Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
| | - Alan R Brash
- Department of Pharmacology and the Vanderbilt Institute of Chemical Biology, Vanderbilt University School of Medicine, Nashville, TN 37232, USA.
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