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Nakanishi K, Li H, Ichino T, Tatsumi K, Osakabe K, Watanabe B, Shimomura K, Yazaki K. Peroxisomal 4-coumaroyl-CoA ligases participate in shikonin production in Lithospermum erythrorhizon. PLANT PHYSIOLOGY 2024; 195:2843-2859. [PMID: 38478427 DOI: 10.1093/plphys/kiae157] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/06/2024] [Accepted: 02/18/2024] [Indexed: 08/02/2024]
Abstract
4-Coumaroyl-CoA ligase (4CL) is a key enzyme in the phenylpropanoid pathway, which is involved in the biosynthesis of various specialized metabolites such as flavonoids, coumarins, lignans, and lignin. Plants have several 4CLs showing divergence in sequence: Class I 4CLs involved in lignin metabolism, Class II 4CLs associated with flavonoid metabolism, and atypical 4CLs and 4CL-like proteins of unknown function. Shikonin, a Boraginaceae-specific specialized metabolite in red gromwell (Lithospermum erythrorhizon), is biosynthesized from p-hydroxybenzoic acid, and the involvement of 4CL in its biosynthesis has long been debated. In this study, we demonstrated the requirement of 4CL for shikonin biosynthesis using a 4CL-specific inhibitor. In silico analysis of the L. erythrorhizon genome revealed the presence of at least 8 4CL genes, among which the expression of 3 (Le4CL3, Le4CL4, and Le4CL5) showed a positive association with shikonin production. Phylogenetic analysis indicated that Le4CL5 belongs to Class I 4CLs, while Le4CL3 and Le4CL4 belong to clades that are distant from Class I and Class II. Interestingly, both Le4CL3 and Le4CL4 have peroxisome targeting signal 1 in their C-terminal region, and subcellular localization analysis revealed that both localize to the peroxisome. We targeted each of the 3 Le4CL genes by CRISPR/Cas9-mediated mutagenesis and observed remarkably lower shikonin production in Le4CL3-ge and Le4CL4-ge genome-edited lines compared with the vector control. We, therefore, conclude that peroxisomal Le4CL3 and Le4CL4 are responsible for shikonin production and propose a model for metabolite-specific 4CL distribution in L. erythrorhizon.
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Affiliation(s)
- Kohei Nakanishi
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Hao Li
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Takuji Ichino
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
- Laboratory of Medicinal Cell Biology, Kobe Pharmaceutical University, Kobe, Hyogo 658-8558, Japan
| | - Kanade Tatsumi
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
| | - Keishi Osakabe
- Graduate School of Technology, Industrial and Social Science, Tokushima University, Tokushima, Tokushima 770-8503, Japan
| | - Bunta Watanabe
- Chemistry Laboratory, The Jikei University School of Medicine, Chofu, Tokyo 182-8570, Japan
| | - Koichiro Shimomura
- Graduate School of Life Science, Toyo University, 1-1-1 Izumino, Itakura, Ora, Gunma 374-0193, Japan
| | - Kazufumi Yazaki
- Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan
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Shin D, Cho KH, Tucker E, Yoo CY, Kim J. Identification of tomato F-box proteins functioning in phenylpropanoid metabolism. PLANT MOLECULAR BIOLOGY 2024; 114:85. [PMID: 38995464 DOI: 10.1007/s11103-024-01483-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2024] [Accepted: 06/26/2024] [Indexed: 07/13/2024]
Abstract
Phenylpropanoids, a class of specialized metabolites, play crucial roles in plant growth and stress adaptation and include diverse phenolic compounds such as flavonoids. Phenylalanine ammonia-lyase (PAL) and chalcone synthase (CHS) are essential enzymes functioning at the entry points of general phenylpropanoid biosynthesis and flavonoid biosynthesis, respectively. In Arabidopsis, PAL and CHS are turned over through ubiquitination-dependent proteasomal degradation. Specific kelch domain-containing F-Box (KFB) proteins as components of ubiquitin E3 ligase directly interact with PAL or CHS, leading to polyubiquitinated PAL and CHS, which in turn influences phenylpropanoid and flavonoid production. Although phenylpropanoids are vital for tomato nutritional value and stress responses, the post-translational regulation of PAL and CHS in tomato remains unknown. We identified 31 putative KFB-encoding genes in the tomato genome. Our homology analysis and phylogenetic study predicted four PAL-interacting SlKFBs, while SlKFB18 was identified as the sole candidate for the CHS-interacting KFB. Consistent with their homolog function, the predicted four PAL-interacting SlKFBs function in PAL degradation. Surprisingly, SlKFB18 did not interact with tomato CHS and the overexpression or knocking out of SlKFB18 did not affect phenylpropanoid contents in tomato transgenic lines, suggesting its irreverence with flavonoid metabolism. Our study successfully discovered the post-translational regulatory machinery of PALs in tomato while highlighting the limitation of relying solely on a homology-based approach to predict interacting partners of F-box proteins.
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Affiliation(s)
- Doosan Shin
- Horticultural Sciences Department, University of Florida, Gainesville, FL, 32611, USA
| | - Keun Ho Cho
- Horticultural Sciences Department, University of Florida, Gainesville, FL, 32611, USA
| | - Ethan Tucker
- Plant Molecular and Cellular Biology Graduate Program, University of Florida, Gainesville, FL, USA
| | - Chan Yul Yoo
- School of Biological Sciences, University of Utah, Salt Lake City, UT, 84112, USA
| | - Jeongim Kim
- Horticultural Sciences Department, University of Florida, Gainesville, FL, 32611, USA.
- Plant Molecular and Cellular Biology Graduate Program, University of Florida, Gainesville, FL, USA.
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Rudenko NN, Vetoshkina DV, Marenkova TV, Borisova-Mubarakshina MM. Antioxidants of Non-Enzymatic Nature: Their Function in Higher Plant Cells and the Ways of Boosting Their Biosynthesis. Antioxidants (Basel) 2023; 12:2014. [PMID: 38001867 PMCID: PMC10669185 DOI: 10.3390/antiox12112014] [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: 10/24/2023] [Revised: 11/14/2023] [Accepted: 11/15/2023] [Indexed: 11/26/2023] Open
Abstract
Plants are exposed to a variety of abiotic and biotic stresses leading to increased formation of reactive oxygen species (ROS) in plant cells. ROS are capable of oxidizing proteins, pigments, lipids, nucleic acids, and other cell molecules, disrupting their functional activity. During the process of evolution, numerous antioxidant systems were formed in plants, including antioxidant enzymes and low molecular weight non-enzymatic antioxidants. Antioxidant systems perform neutralization of ROS and therefore prevent oxidative damage of cell components. In the present review, we focus on the biosynthesis of non-enzymatic antioxidants in higher plants cells such as ascorbic acid (vitamin C), glutathione, flavonoids, isoprenoids, carotenoids, tocopherol (vitamin E), ubiquinone, and plastoquinone. Their functioning and their reactivity with respect to individual ROS will be described. This review is also devoted to the modern genetic engineering methods, which are widely used to change the quantitative and qualitative content of the non-enzymatic antioxidants in cultivated plants. These methods allow various plant lines with given properties to be obtained in a rather short time. The most successful approaches for plant transgenesis and plant genome editing for the enhancement of biosynthesis and the content of these antioxidants are discussed.
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Affiliation(s)
- Natalia N. Rudenko
- Institute of Basic Biological Problems, Federal Research Center “Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences”, Pushchino 142290, Russia; (D.V.V.); (M.M.B.-M.)
| | - Daria V. Vetoshkina
- Institute of Basic Biological Problems, Federal Research Center “Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences”, Pushchino 142290, Russia; (D.V.V.); (M.M.B.-M.)
| | - Tatiana V. Marenkova
- Federal Research Center Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences, Novosibirsk 630090, Russia;
| | - Maria M. Borisova-Mubarakshina
- Institute of Basic Biological Problems, Federal Research Center “Pushchino Scientific Center for Biological Research of the Russian Academy of Sciences”, Pushchino 142290, Russia; (D.V.V.); (M.M.B.-M.)
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Niñoles R, Arjona P, Azad SM, Hashim A, Casañ J, Bueso E, Serrano R, Espinosa A, Molina I, Gadea J. Kaempferol-3-rhamnoside overaccumulation in flavonoid 3'-hydroxylase tt7 mutants compromises seed coat outer integument differentiation and seed longevity. THE NEW PHYTOLOGIST 2023; 238:1461-1478. [PMID: 36829299 DOI: 10.1111/nph.18836] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 02/21/2023] [Indexed: 06/18/2023]
Abstract
Seeds slowly accumulate damage during storage, which ultimately results in germination failure. The seed coat protects the embryo from the external environment, and its composition is critical for seed longevity. Flavonols accumulate in the outer integument. The link between flavonol composition and outer integument development has not been explored. Genetic, molecular and ultrastructural assays on loss-of-function mutants of the flavonoid biosynthesis pathway were used to study the effect of altered flavonoid composition on seed coat development and seed longevity. Controlled deterioration assays indicate that loss of function of the flavonoid 3' hydroxylase gene TT7 dramatically affects seed longevity and seed coat development. Outer integument differentiation is compromised from 9 d after pollination in tt7 developing seeds, resulting in a defective suberin layer and incomplete degradation of seed coat starch. These distinctive phenotypes are not shared by other mutants showing abnormal flavonoid composition. Genetic analysis indicates that overaccumulation of kaempferol-3-rhamnoside is mainly responsible for the observed phenotypes. Expression profiling suggests that multiple cellular processes are altered in the tt7 mutant. Overaccumulation of kaempferol-3-rhamnoside in the seed coat compromises normal seed coat development. This observation positions TRANSPARENT TESTA 7 and the UGT78D1 glycosyltransferase, catalysing flavonol 3-O-rhamnosylation, as essential players in the modulation of seed longevity.
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Affiliation(s)
- Regina Niñoles
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universitat Politècnica de València (UPV)-Consejo Superior de Investigaciones Científicas (CSIC), Ciudad Politécnica de la Innovación (CPI), Ed. 8E, C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
| | - Paloma Arjona
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universitat Politècnica de València (UPV)-Consejo Superior de Investigaciones Científicas (CSIC), Ciudad Politécnica de la Innovación (CPI), Ed. 8E, C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
| | - Sepideh M Azad
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universitat Politècnica de València (UPV)-Consejo Superior de Investigaciones Científicas (CSIC), Ciudad Politécnica de la Innovación (CPI), Ed. 8E, C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
| | - Aseel Hashim
- Department of Biology, Algoma University, 1520 Queen Street East, Sault Ste. Marie, ON, P6A 2G4, Canada
| | - Jose Casañ
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universitat Politècnica de València (UPV)-Consejo Superior de Investigaciones Científicas (CSIC), Ciudad Politécnica de la Innovación (CPI), Ed. 8E, C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
| | - Eduardo Bueso
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universitat Politècnica de València (UPV)-Consejo Superior de Investigaciones Científicas (CSIC), Ciudad Politécnica de la Innovación (CPI), Ed. 8E, C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
| | - Ramón Serrano
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universitat Politècnica de València (UPV)-Consejo Superior de Investigaciones Científicas (CSIC), Ciudad Politécnica de la Innovación (CPI), Ed. 8E, C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
| | - Ana Espinosa
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universitat Politècnica de València (UPV)-Consejo Superior de Investigaciones Científicas (CSIC), Ciudad Politécnica de la Innovación (CPI), Ed. 8E, C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
| | - Isabel Molina
- Department of Biology, Algoma University, 1520 Queen Street East, Sault Ste. Marie, ON, P6A 2G4, Canada
| | - Jose Gadea
- Instituto de Biología Molecular y Celular de Plantas (IBMCP), Universitat Politècnica de València (UPV)-Consejo Superior de Investigaciones Científicas (CSIC), Ciudad Politécnica de la Innovación (CPI), Ed. 8E, C/Ingeniero Fausto Elio s/n, 46022, Valencia, Spain
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Xu JJ, Hu M, Yang L, Chen XY. How plants synthesize coenzyme Q. PLANT COMMUNICATIONS 2022; 3:100341. [PMID: 35614856 PMCID: PMC9483114 DOI: 10.1016/j.xplc.2022.100341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/11/2022] [Revised: 05/04/2022] [Accepted: 05/19/2022] [Indexed: 06/15/2023]
Abstract
Coenzyme Q (CoQ) is a conserved redox-active lipid that has a wide distribution across the domains of life. CoQ plays a key role in the oxidative electron transfer chain and serves as a crucial antioxidant in cellular membranes. Our understanding of CoQ biosynthesis in eukaryotes has come mostly from studies of yeast. Recently, significant advances have been made in understanding CoQ biosynthesis in plants. Unique mitochondrial flavin-dependent monooxygenase and benzenoid ring precursor biosynthetic pathways have been discovered, providing new insights into the diversity of CoQ biosynthetic pathways and the evolution of phototrophic eukaryotes. We summarize research progress on CoQ biosynthesis and regulation in plants and recent efforts to increase the CoQ content in plant foods.
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Affiliation(s)
- Jing-Jing Xu
- Shanghai Key Laboratory of Plant Functional Genomics and Resources, Shanghai Chenshan Botanical Garden, Shanghai 201602, China; Chenshan Plant Science Research Center, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 201602, China.
| | - Mei Hu
- Shanghai Key Laboratory of Plant Functional Genomics and Resources, Shanghai Chenshan Botanical Garden, Shanghai 201602, China; Co-Innovation Center for Sustainable Forestry in Southern China, College of Biology and the Environment, Nanjing Forestry University, Nanjing 210037, China
| | - Lei Yang
- Shanghai Key Laboratory of Plant Functional Genomics and Resources, Shanghai Chenshan Botanical Garden, Shanghai 201602, China; Chenshan Plant Science Research Center, CAS Center for Excellence in Molecular Plant Sciences, Chinese Academy of Sciences, Shanghai 201602, China
| | - Xiao-Ya Chen
- Shanghai Key Laboratory of Plant Functional Genomics and Resources, Shanghai Chenshan Botanical Garden, Shanghai 201602, China; State Key Laboratory of Plant Molecular Genetics, CAS Center for Excellence in Molecular Plant Sciences/Shanghai Institute of Plant Physiology and Ecology, University of CAS, Chinese Academy of Sciences, Shanghai 200032, China
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Berger A, Latimer S, Stutts LR, Soubeyrand E, Block AK, Basset GJ. Kaempferol as a precursor for ubiquinone (coenzyme Q) biosynthesis: An atypical node between specialized metabolism and primary metabolism. CURRENT OPINION IN PLANT BIOLOGY 2022; 66:102165. [PMID: 35026487 DOI: 10.1016/j.pbi.2021.102165] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Revised: 11/15/2021] [Accepted: 12/01/2021] [Indexed: 05/23/2023]
Abstract
Ubiquinone (coenzyme Q) is a vital respiratory cofactor and liposoluble antioxidant. Studies have shown that plants derive approximately a quarter of 4-hydroxybenzoate, which serves as the direct ring precursor of ubiquinone, from the catabolism of kaempferol. Biochemical and genetic evidence suggests that the release of 4-hydroxybenzoate from kaempferol is catalyzed by heme-dependent peroxidases and that 3-O-glycosylations of kaempferol act as a negative regulator of this process. These findings not only represent an atypical instance of primary metabolite being derived from specialized metabolism but also raise the question as to whether ubiquinone contributes to the ROS scavenging and signaling functions already established for flavonols.
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Affiliation(s)
- Antoine Berger
- Department of Horticultural Sciences, University of Florida, Gainesville, FL, 32611, USA
| | - Scott Latimer
- Department of Horticultural Sciences, University of Florida, Gainesville, FL, 32611, USA
| | - Lauren R Stutts
- Department of Horticultural Sciences, University of Florida, Gainesville, FL, 32611, USA
| | - Eric Soubeyrand
- Department of Horticultural Sciences, University of Florida, Gainesville, FL, 32611, USA
| | - Anna K Block
- Center for Medical, Agricultural and Veterinary Entomology, Chemistry Research Unit, ARS, USDA, Gainesville, FL, 32608, USA
| | - Gilles J Basset
- Department of Horticultural Sciences, University of Florida, Gainesville, FL, 32611, USA.
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Latimer S, Keene SA, Stutts LR, Berger A, Bernert AC, Soubeyrand E, Wright J, Clarke CF, Block AK, Colquhoun TA, Elowsky C, Christensen A, Wilson MA, Basset GJ. A dedicated flavin-dependent monooxygenase catalyzes the hydroxylation of demethoxyubiquinone into ubiquinone (coenzyme Q) in Arabidopsis. J Biol Chem 2021; 297:101283. [PMID: 34626646 PMCID: PMC8559556 DOI: 10.1016/j.jbc.2021.101283] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 09/30/2021] [Accepted: 10/04/2021] [Indexed: 01/08/2023] Open
Abstract
Ubiquinone (Coenzyme Q) is a vital respiratory cofactor and liposoluble antioxidant. In plants, it is not known how the C-6 hydroxylation of demethoxyubiquinone, the penultimate step in ubiquinone biosynthesis, is catalyzed. The combination of cross-species gene network modeling along with mining of embryo-defective mutant databases of Arabidopsis thaliana identified the embryo lethal locus EMB2421 (At1g24340) as a top candidate for the missing plant demethoxyubiquinone hydroxylase. In marked contrast with prototypical eukaryotic demethoxyubiquinone hydroxylases, the catalytic mechanism of which depends on a carboxylate-bridged di-iron domain, At1g24340 is homologous to FAD-dependent oxidoreductases that instead use NAD(P)H as an electron donor. Complementation assays in Saccharomyces cerevisiae and Escherichia coli demonstrated that At1g24340 encodes a functional demethoxyubiquinone hydroxylase and that the enzyme displays strict specificity for the C-6 position of the benzoquinone ring. Laser-scanning confocal microscopy also showed that GFP-tagged At1g24340 is targeted to mitochondria. Silencing of At1g24340 resulted in 40 to 74% decrease in ubiquinone content and de novo ubiquinone biosynthesis. Consistent with the role of At1g24340 as a benzenoid ring modification enzyme, this metabolic blockage could not be bypassed by supplementation with 4-hydroxybenzoate, the immediate precursor of ubiquinone's ring. Unlike in yeast, in Arabidopsis overexpression of demethoxyubiquinone hydroxylase did not boost ubiquinone content. Phylogenetic reconstructions indicated that plant demethoxyubiquinone hydroxylase is most closely related to prokaryotic monooxygenases that act on halogenated aromatics and likely descends from an event of horizontal gene transfer between a green alga and a bacterium.
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Affiliation(s)
- Scott Latimer
- Department of Horticultural Sciences, University of Florida, Gainesville, Florida, USA.
| | - Shea A Keene
- Department of Environmental Horticulture, Plant Innovation Center, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, USA
| | - Lauren R Stutts
- Department of Horticultural Sciences, University of Florida, Gainesville, Florida, USA
| | - Antoine Berger
- Department of Horticultural Sciences, University of Florida, Gainesville, Florida, USA
| | - Ann C Bernert
- Department of Horticultural Sciences, University of Florida, Gainesville, Florida, USA
| | - Eric Soubeyrand
- Department of Horticultural Sciences, University of Florida, Gainesville, Florida, USA
| | - Janet Wright
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | - Catherine F Clarke
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, California, USA
| | - Anna K Block
- Center for Medical, Agricultural and Veterinary Entomology, Chemistry Research Unit, ARS, USDA, Gainesville, Florida, USA
| | - Thomas A Colquhoun
- Department of Environmental Horticulture, Plant Innovation Center, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, Florida, USA
| | - Christian Elowsky
- Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | - Alan Christensen
- School of Biological Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | - Mark A Wilson
- Department of Biochemistry and Redox Biology Center, University of Nebraska-Lincoln, Lincoln, Nebraska, USA
| | - Gilles J Basset
- Department of Horticultural Sciences, University of Florida, Gainesville, Florida, USA.
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Fernández-del-Río L, Clarke CF. Coenzyme Q Biosynthesis: An Update on the Origins of the Benzenoid Ring and Discovery of New Ring Precursors. Metabolites 2021; 11:385. [PMID: 34198496 PMCID: PMC8231959 DOI: 10.3390/metabo11060385] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2021] [Revised: 06/06/2021] [Accepted: 06/08/2021] [Indexed: 12/17/2022] Open
Abstract
Coenzyme Q (ubiquinone or CoQ) is a conserved polyprenylated lipid essential for mitochondrial respiration. CoQ is composed of a redox-active benzoquinone ring and a long polyisoprenyl tail that serves as a membrane anchor. A classic pathway leading to CoQ biosynthesis employs 4-hydroxybenzoic acid (4HB). Recent studies with stable isotopes in E. coli, yeast, and plant and animal cells have identified CoQ intermediates and new metabolic pathways that produce 4HB. Stable isotope labeling has identified para-aminobenzoic acid as an alternate ring precursor of yeast CoQ biosynthesis, as well as other natural products, such as kaempferol, that provide ring precursors for CoQ biosynthesis in plants and mammals. In this review, we highlight how stable isotopes can be used to delineate the biosynthetic pathways leading to CoQ.
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Affiliation(s)
| | - Catherine F. Clarke
- Department of Chemistry and Biochemistry and the Molecular Biology Institute, University of California, Los Angeles, CA 90095-1569, USA;
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