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Kazachkov M, Li Q, Shen W, Wang L, Gao P, Xiang D, Datla R, Zou J. Molecular identification and functional characterization of a cyanogenic glucosyltransferase from flax (Linum unsitatissimum). PLoS One 2020; 15:e0227840. [PMID: 32023283 PMCID: PMC7001965 DOI: 10.1371/journal.pone.0227840] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Accepted: 12/30/2019] [Indexed: 11/18/2022] Open
Abstract
Flax seed has become consumers’ choice for not only polyunsaturated alpha-linolenic fatty acid but also nutraceuticals such as lignans and soluble fiber. There is, however, a major drawback of flax as a source of functional food since the seeds contain significant level of cyanogenic glucosides. The final step of cyanogenic glucoside biosynthesis is mediated by UDP-glucose dependent glucosyltransferase. To date, no flax cyanogenic glucosyl transferase genes have been reported with verified biochemical functionality. Here we present a study on the identification and enzymatic characterization of a first flax cyanogenic glucosyltransferase, LuCGT1. We show that LuCGT1 was highly active towards both aliphatic and aromatic substrates. The LuCGT1 gene is expressed in leaf tissues as well as in developing seeds, and its expression level was drastically reduced in flax mutant lines low in cyanogenic glucosides. Identification of LuCGT1 provides a molecular handle for developing gene specific markers for targeted breeding of low cyanogenic glucosides in flax.
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Affiliation(s)
| | - Qiang Li
- National Research Council Canada, Saskatoon, Saskatchewan, Canada
- Department of Plant Science, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Wenyun Shen
- National Research Council Canada, Saskatoon, Saskatchewan, Canada
| | - Liping Wang
- National Research Council Canada, Saskatoon, Saskatchewan, Canada
| | - Peng Gao
- National Research Council Canada, Saskatoon, Saskatchewan, Canada
| | - Daoquan Xiang
- National Research Council Canada, Saskatoon, Saskatchewan, Canada
| | - Raju Datla
- National Research Council Canada, Saskatoon, Saskatchewan, Canada
| | - Jitao Zou
- National Research Council Canada, Saskatoon, Saskatchewan, Canada
- * E-mail:
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Ehlert M, Jagd LM, Braumann I, Dockter C, Crocoll C, Motawia MS, Møller BL, Lyngkjær MF. Deletion of biosynthetic genes, specific SNP patterns and differences in transcript accumulation cause variation in hydroxynitrile glucoside content in barley cultivars. Sci Rep 2019; 9:5730. [PMID: 30952890 PMCID: PMC6450869 DOI: 10.1038/s41598-019-41884-w] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2018] [Accepted: 03/15/2019] [Indexed: 11/09/2022] Open
Abstract
Barley (Hordeum vulgare L.) produces five leucine-derived hydroxynitrile glucosides, potentially involved in alleviating pathogen and environmental stresses. These compounds include the cyanogenic glucoside epiheterodendrin. The biosynthetic genes are clustered. Total hydroxynitrile glucoside contents were previously shown to vary from zero to more than 10,000 nmoles g-1 in different barley lines. To elucidate the cause of this variation, the biosynthetic genes from the high-level producer cv. Mentor, the medium-level producer cv. Pallas, and the zero-level producer cv. Emir were investigated. In cv. Emir, a major deletion in the genome spanning most of the hydroxynitrile glucoside biosynthetic gene cluster was identified and explains the complete absence of hydroxynitrile glucosides in this cultivar. The transcript levels of the biosynthetic genes were significantly higher in the high-level producer cv. Mentor compared to the medium-level producer cv. Pallas, indicating transcriptional regulation as a contributor to the variation in hydroxynitrile glucoside levels. A correlation between distinct single nucleotide polymorphism (SNP) patterns in the biosynthetic gene cluster and the hydroxynitrile glucoside levels in 227 barley lines was identified. It is remarkable that in spite of the demonstrated presence of a multitude of SNPs and differences in transcript levels, the ratio between the five hydroxynitrile glucosides is maintained across all the analysed barley lines. This implies the involvement of a stably assembled multienzyme complex.
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Affiliation(s)
- Marcus Ehlert
- Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Copenhagen, Denmark
- VILLUM Research Center for Plant Plasticity, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Copenhagen, Denmark
| | - Lea Møller Jagd
- Carlsberg Research Laboratory, J.C. Jacobsens Gade 4, 1799, Copenhagen V, Denmark
| | - Ilka Braumann
- Carlsberg Research Laboratory, J.C. Jacobsens Gade 4, 1799, Copenhagen V, Denmark
| | - Christoph Dockter
- Carlsberg Research Laboratory, J.C. Jacobsens Gade 4, 1799, Copenhagen V, Denmark
| | - Christoph Crocoll
- DynaMo Center, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Denmark
| | - Mohammed Saddik Motawia
- Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Copenhagen, Denmark
- VILLUM Research Center for Plant Plasticity, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Copenhagen, Denmark
| | - Birger Lindberg Møller
- Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Copenhagen, Denmark
- VILLUM Research Center for Plant Plasticity, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Copenhagen, Denmark
- Carlsberg Research Laboratory, J.C. Jacobsens Gade 4, 1799, Copenhagen V, Denmark
| | - Michael Foged Lyngkjær
- Plant Biochemistry Laboratory, Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Copenhagen, Denmark.
- VILLUM Research Center for Plant Plasticity, University of Copenhagen, Thorvaldsensvej 40, 1871, Frederiksberg C, Copenhagen, Denmark.
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3
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Schenck CA, Maeda HA. Tyrosine biosynthesis, metabolism, and catabolism in plants. PHYTOCHEMISTRY 2018; 149:82-102. [PMID: 29477627 DOI: 10.1016/j.phytochem.2018.02.003] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Revised: 01/26/2018] [Accepted: 02/02/2018] [Indexed: 05/22/2023]
Abstract
L-Tyrosine (Tyr) is an aromatic amino acid (AAA) required for protein synthesis in all organisms, but synthesized de novo only in plants and microorganisms. In plants, Tyr also serves as a precursor of numerous specialized metabolites that have diverse physiological roles as electron carriers, antioxidants, attractants, and defense compounds. Some of these Tyr-derived plant natural products are also used in human medicine and nutrition (e.g. morphine and vitamin E). While the Tyr biosynthesis and catabolic pathways have been extensively studied in microbes and animals, respectively, those of plants have received much less attention until recently. Accumulating evidence suggest that the Tyr biosynthetic pathways differ between microbes and plants and even within the plant kingdom, likely to support the production of lineage-specific plant specialized metabolites derived from Tyr. The interspecies variations of plant Tyr pathway enzymes can now be used to enhance the production of Tyr and Tyr-derived compounds in plants and other synthetic biology platforms.
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Affiliation(s)
- Craig A Schenck
- Department of Botany, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Hiroshi A Maeda
- Department of Botany, University of Wisconsin-Madison, Madison, WI 53706, USA.
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Yamaguchi T, Kuwahara Y, Asano Y. A novel cytochrome P450, CYP3201B1, is involved in ( R)-mandelonitrile biosynthesis in a cyanogenic millipede. FEBS Open Bio 2017; 7:335-347. [PMID: 28286729 PMCID: PMC5337904 DOI: 10.1002/2211-5463.12170] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 11/16/2016] [Accepted: 11/18/2016] [Indexed: 12/31/2022] Open
Abstract
Specialized arthropods and more than 2500 plant species biosynthesize hydroxynitriles and release hydrogen cyanide as a defensive mechanism. The millipede Chamberlinius hualienensis accumulates (R)-mandelonitrile as a cyanide precursor. Although biosynthesis of hydroxynitriles in cyanogenic plants and in an insect are extensively studied, (R)-mandelonitrile biosynthesis in cyanogenic millipedes has remained unclear. In this study, we identified the biosynthetic precursors of (R)-mandelonitrile and an enzyme involved in (R)-mandelonitrile biosynthesis. Using deuterium-labelled compounds, we revealed that (E/Z)-phenylacetaldoxime and phenylacetonitrile are the biosynthetic precursors of (R)-mandelonitrile in the millipede as well as other cyanogenic organisms. To identify the enzymes involved in (R)-mandelonitrile biosynthesis, 50 cDNAs encoding cytochrome P450s were cloned and coexpressed with yeast cytochrome P450 reductase in yeast, as cytochrome P450s are involved in the biosynthesis of hydroxynitriles in other cyanogenic organisms. Among the 50 cytochrome P450s from the millipede, CYP3201B1 produced (R)-mandelonitrile from phenylacetonitrile but not from (E/Z)-phenylacetaldoxime, whereas plant and insect cytochrome P450s catalysed the dehydration of aldoximes and hydroxylation of nitriles. CYP3201B1 is not phylogenetically related to cytochrome P450s from other cyanogenic organisms, indicating that hydroxynitrile biosynthetic cytochrome P450s have independently evolved in distant species. Our study will shed light on the evolution of cyanogenesis among plants, insects and millipedes. DATABASE Nucleotide sequence data are available in the DDBJ/EMBL/GenBank databases under the accession numbers LC125356-LC125405.
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Affiliation(s)
- Takuya Yamaguchi
- Biotechnology Research Center and Department of BiotechnologyToyama Prefectural UniversityImizuJapan
- JSTERATOAsano Active Enzyme Molecule ProjectImizuJapan
| | - Yasumasa Kuwahara
- Biotechnology Research Center and Department of BiotechnologyToyama Prefectural UniversityImizuJapan
- JSTERATOAsano Active Enzyme Molecule ProjectImizuJapan
| | - Yasuhisa Asano
- Biotechnology Research Center and Department of BiotechnologyToyama Prefectural UniversityImizuJapan
- JSTERATOAsano Active Enzyme Molecule ProjectImizuJapan
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5
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Ethnobotany and phytochemistry of plants dominant in salt marshes of the Lower Saxonian Wadden Sea, southern North Sea. ACTA ACUST UNITED AC 2008. [DOI: 10.1007/bf03043865] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Halkier BA, Scheller HV, Møller BL. Cyanogenic glucosides: the biosynthetic pathway and the enzyme system involved. CIBA FOUNDATION SYMPOSIUM 2007; 140:49-66. [PMID: 3073062 DOI: 10.1002/9780470513712.ch5] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
In vitro studies with a microsomal system obtained from etiolated sorghum seedlings have indicated a biosynthetic pathway for cyanogenic glucosides involving amino acids, N-hydroxyamino acids, aldoximes, nitriles and cyanohydrins. NADPH is an essential cofactor. Simultaneous measurements of tyrosine metabolism and oxygen consumption show that three molecules of oxygen are consumed for each molecule of p-hydroxymandelonitrile produced. This indicates the operation of three monooxygenases in the pathway and implies the involvement of one hitherto undetected intermediate in the pathway. The nature of this intermediate is unknown. Gel filtration and sucrose gradient centrifugation of the microsomal system resulted in a more than tenfold increase in specific activity. Attempts to further purify the system did not produce preparations of higher specific activity because of a simultaneous partial loss of essential components as demonstrated by reconstitution experiments.
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Affiliation(s)
- B A Halkier
- Department of Plant Physiology, Royal Veterinary and Agricultural University, Frederiksberg, Denmark
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Kutchan TM. A role for intra- and intercellular translocation in natural product biosynthesis. CURRENT OPINION IN PLANT BIOLOGY 2005; 8:292-300. [PMID: 15860426 DOI: 10.1016/j.pbi.2005.03.009] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The formation and storage of plant natural products such as phenylpropanoids, terpenoids and alkaloids are dynamic and complex processes that involve multiple subcellular compartments and cell types. Evidence is emerging to show that consecutive enzymes of phenylpropanoid and flavonoid biosynthesis are organized into macromolecular complexes that can be associated with endomembranes, that monoterpenoid biosynthetic enzymes are exclusively localized to highly specialized glandular trichome secretory cells and that complex monoterpenoid indole- and morphinan alkaloids require a combination of phloem parenchyma, laticifers and epidermal cells for their synthesis and storage. Highly ordered, protein-mediated processes that involve intra- and intercellular translocation need be considered when attempting to understand how a plant can regulate the formation and accumulation of complex but well-defined natural product profiles.
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Affiliation(s)
- Toni M Kutchan
- Leibniz-Institut für Pflanzenbiochemie, Weinberg 3, 06120 Halle/Saale, Germany.
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Busk PK, Møller BL. Dhurrin synthesis in sorghum is regulated at the transcriptional level and induced by nitrogen fertilization in older plants. PLANT PHYSIOLOGY 2002; 129:1222-31. [PMID: 12114576 PMCID: PMC166516 DOI: 10.1104/pp.000687] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/01/2001] [Revised: 02/01/2002] [Accepted: 03/08/2002] [Indexed: 05/18/2023]
Abstract
The content of the cyanogenic glucoside dhurrin in sorghum (Sorghum bicolor L. Moench) varies depending on plant age and growth conditions. The cyanide potential is highest shortly after onset of germination. At this stage, nitrogen application has no effect on dhurrin content, whereas in older plants, nitrogen application induces an increase. At all stages, the content of dhurrin correlates well with the activity of the two biosynthetic enzymes, CYP79A1 and CYP71E1, and with the protein and mRNA level for the two enzymes. During development, the activity of CYP79A1 is lower than the activity of CYP71E1, suggesting that CYP79A1 catalyzes the rate-limiting step in dhurrin synthesis as has previously been shown using etiolated seedlings. The site of dhurrin synthesis shifts from leaves to stem during plant development. In combination, the results demonstrate that dhurrin content in sorghum is largely determined by transcriptional regulation of the biosynthetic enzymes CYP79A1 and CYP71E1.
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Affiliation(s)
- Peter Kamp Busk
- Plant Biochemistry Laboratory, Department of Plant Biology, and Center for Molecular Plant Physiology, Royal Veterinary and Agricultural University, 40 Thorvaldsensvej, DK-1871 Frederiksberg C, Copenhagen, Denmark
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9
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Dixon RA, Chen F, Guo D, Parvathi K. The biosynthesis of monolignols: a "metabolic grid", or independent pathways to guaiacyl and syringyl units? PHYTOCHEMISTRY 2001; 57:1069-84. [PMID: 11430980 DOI: 10.1016/s0031-9422(01)00092-9] [Citation(s) in RCA: 80] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Lignin is a complex polymer formed by the oxidative polymerization of hydroxycinnamyl alcohol derivatives termed monolignols. The major monolignols in dicotyledonous angiosperm lignin are monomethylated guaiacyl (G) units derived from coniferyl alcohol, and dimethylated syringyl (S) units derived from sinapyl alcohol. The biochemical pathways leading to the formation of monolignols feature successive hydroxylation and O-methylation of the aromatic ring and conversion of the side chain carboxyl to an alcohol function. The current view of the monolignol biosynthetic pathway envisages a metabolic grid leading to G and S units, through which the successive hydroxylation and O-methylation reactions may occur at different levels of side chain oxidation. The present article assesses biochemical and genetic evidence for and against such a model, including recent data on the methylation reactions of monolignol biosynthesis in alfalfa. We draw attention to portions of the currently accepted monolignol pathway that may require revision, and suggest an alternative model in which metabolic channeling allows for independent pathways to G and S lignin.
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Affiliation(s)
- R A Dixon
- Plant Biology Division, Samuel Roberts Noble Foundation, 2510 Sam Noble Parkway, Ardmore, OK 73401, USA.
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10
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Nielsen JS, Møller BL. Cloning and expression of cytochrome P450 enzymes catalyzing the conversion of tyrosine to p-hydroxyphenylacetaldoxime in the biosynthesis of cyanogenic glucosides in Triglochin maritima. PLANT PHYSIOLOGY 2000; 122:1311-21. [PMID: 10759528 PMCID: PMC58967 DOI: 10.1104/pp.122.4.1311] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/14/1999] [Accepted: 12/28/1999] [Indexed: 05/22/2023]
Abstract
Two cDNA clones encoding cytochrome P450 enzymes belonging to the CYP79 family have been isolated from Triglochin maritima. The two proteins show 94% sequence identity and have been designated CYP79E1 and CYP79E2. Heterologous expression of the native and the truncated forms of the two clones in Escherichia coli demonstrated that both encode multifunctional N-hydroxylases catalyzing the conversion of tyrosine to p-hydroxyphenylacetaldoxime in the biosynthesis of the two cyanogenic glucosides taxiphyllin and triglochinin in T. maritima. This renders CYP79E functionally identical to CYP79A1 from Sorghum bicolor, and unambiguously demonstrates that cyanogenic glucoside biosynthesis in T. maritima and S. bicolor is catalyzed by analogous enzyme systems with p-hydroxyphenylacetaldoxime as a free intermediate. This is in contrast to earlier reports stipulating p-hydroxyphenylacetonitrile as the only free intermediate in T. maritima. L-3,4-Dihydroxyphenyl[3-(14)C]Ala (DOPA) was not metabolized by CYP79E1, indicating that hydroxylation of the phenol ring at the meta position, as required for triglochinin formation, takes place at a later stage. In S. bicolor, CYP71E1 catalyzes the subsequent conversion of p-hydroxyphenylacetaldoxime to p-hydroxymandelonitrile. When CYP79E1 from T. maritima was reconstituted with CYP71E1 and NADPH-cytochrome P450 oxidoreductase from S. bicolor, efficient conversion of tyrosine to p-hydroxymandelonitrile was observed.
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Affiliation(s)
- J S Nielsen
- Plant Biochemistry Laboratory, Department of Plant Biology and Center for Molecular Plant Physiology (PlaCe), The Royal Veterinary and Agricultural University, 40 Thorvaldsensvej, DK-1871 Frederiksberg C, Copenhagen, Denmark
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11
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The Biosynthesis, Degradation, Transport and Possible Function of Cyanogenic Glucosides. EVOLUTION OF METABOLIC PATHWAYS 2000. [DOI: 10.1016/s0079-9920(00)80008-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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12
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Nielsen JS, Moller BL. Biosynthesis of cyanogenic glucosides in Triglochin maritima and the involvement of cytochrome P450 enzymes. Arch Biochem Biophys 1999; 368:121-30. [PMID: 10415119 DOI: 10.1006/abbi.1999.1258] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The biosynthesis of the two cyanogenic glucosides, taxiphyllin and triglochinin, in Triglochin maritima (seaside arrow grass) has been studied using undialyzed microsomal preparations from flowers and fruits. Tyrosine was converted to p-hydroxymandelonitrile with V(max) and K(m) values of 36 nmol mg(-1) g(-1) fresh weight and 0.14 mM, respectively. p-Hydroxyphenylacetaldoxime and p-hydroxyphenylacetonitrile accumulated as intermediates in the reaction mixtures. Using radiolabeled tyrosine as substrate, the radiolabel was easily trapped in p-hydroxyphenylacetaldoxime and p-hydroxyphenylacetonitrile when these were added as unlabeled compounds. p-Hydroxyphenylacetaldoxime was the only product obtained using microsomes prepared from green leaves or dialyzed microsomes prepared from flowers and fruits. These data contrast earlier reports (Hösel and Nahrstedt, Arch. Biochem. Biophys. 203, 753-757, 1980; and Cutler et al., J. Biol. Chem. 256, 4253-4258, 1981) where p-hydroxyphenylacetaldoxime was found not to accumulate. All steps in the conversion of tyrosine to p-hydroxymandelonitrile were found to be catalyzed by cytochrome P450 enzymes as documented by photoreversible carbon monoxide inhibition, inhibition by antibodies toward NADPH-cytochrome P450 oxidoreductase, and by cytochrome P450 inhibitors. We hypothesize that cyanogenic glucoside synthesis in T. maritima is catalyzed by multifunctional cytochrome P450 enzymes similar to CYP79A1 and CYP71E1 in Sorghum bicolor except that the homolog to CYP71E1 in T. maritima exhibits a less tight binding of p-hydroxyphenylacetonitrile, thus permitting the release of this intermediate and its conversion into triglochinin.
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Affiliation(s)
- J S Nielsen
- Department of Plant Biology, Center for Molecular Plant Physiology (PlaCe), The Royal Veterinary and Agricultural University, 40 Thorvaldsensvej, Copenhagen, Frederiksberg C, DK-1871, Denmark
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Koch B, Nielsen VS, Halkier BA, Olsen CE, Møller BL. The biosynthesis of cyanogenic glucosides in seedlings of cassava (Manihot esculenta Crantz). Arch Biochem Biophys 1992; 292:141-50. [PMID: 1727632 DOI: 10.1016/0003-9861(92)90062-2] [Citation(s) in RCA: 76] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A microsomal system catalyzing the in vitro synthesis of the aglycones of the two cyanogenic glucosides linamarin and lotaustralin has been isolated from young etiolated seedlings of cassava (Manihot esculenta Crantz). A prerequisite to obtain active preparations is the complete removal of the endosperm pellicle covering the cotyledons before seedling homogenization. The rates of conversion of the parent amino acids valine and isoleucine to their cyanohydrins are 19 and 6 nmol/h/mg protein, respectively. The conversion rates for the corresponding oximes (2-methylpropanal oxime and 2-methylbutanal oxime) are 475 and 440 nmol/h/mg protein and for the nitriles (2-methylpropionitrile and 2-methylbutyronitrile) 45 and 75 nmol/h/mg protein. With the exception of 2-cyclopentenylglycine, none of the additionally tested amino acids are metabolized, whereas a broad substrate specificity is observed using oximes and nitriles as substrates. The in vitro biosynthesis is photoreversibly inhibited by carbon monoxide, demonstrating the involvement of cytochrome P450 in the hydroxylation processes. All tissues of the cassava seedling contain cyanogenic glucosides. The microsomal enzyme system responsible for their synthesis is restricted to the cotyledons and their petioles. This demonstrates that the cyanogenic glucosides are actively transported to other parts of the seedling. The enzyme activity decreases with the height of the etiolated seedling and is barely detectable in seedlings above 75 mm.
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Affiliation(s)
- B Koch
- Department of Plant Biology, Royal Veterinary and Agricultural University, Copenhagen, Denmark
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14
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Halkier BA, Olsen CE, Møller BL. The biosynthesis of cyanogenic glucosides in higher plants. J Biol Chem 1989. [DOI: 10.1016/s0021-9258(19)47140-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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16
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Hösel W, Berlin J, Hanzlik TN, Conn EE. In-vitro biosynthesis of 1-(4'-hydroxyphenyl)-2-nitroethane and production of cyanogenic compounds in osmotically stressed cell suspension cultures of Eschscholtzia californica Cham. PLANTA 1985; 166:176-81. [PMID: 24241429 DOI: 10.1007/bf00397345] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/1985] [Accepted: 06/17/1985] [Indexed: 05/14/2023]
Abstract
Cell suspension cultures of Eschscholtzia californica produce one or more cyanogenic compounds when placed under osmotic stress. The nature of the compound(s) has not yet been established but they are not identical with the cyanogenic glucosides triglochinin and dhurrin, which occur in the intact plant. Microsomal fractions isolated from stressed cell cultures catalyze the synthesis of 1-(4'-hydroxyphenyl)-2-nitroethane from L-tyrosine. Both NADPH and molecular oxygen are required as cosubstrates, and 4-hydroxyphenylacetaldoxime is an intermediate in the synthesis of the nitrocompound. This observation indicates that the biosynthetic pathways leading from L-tyrosine to 1-(4'-hydroxyphenyl)-2-nitroethane and to the L-tyrosine-derived cyanogenic glucosides are closely related. A glucosyltransferase which glucosylates the nitrocompound in the presence of uridine diphosphate glucose appears in the osmotically stressed cultures in a time pattern similar to that for production of the nitrocompound.
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Affiliation(s)
- W Hösel
- Department of Biochemistry and Biophysics, University of California, 95616, Davis, CA, USA
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17
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Cutler AJ, Sternberg M, Conn EE. Properties of a microsomal enzyme system from Linum usitatissimum (linen flax) which oxidizes valine to acetone cyanohydrin and isoleucine to 2-methylbutanone cyanohydrin. Arch Biochem Biophys 1985; 238:272-9. [PMID: 3985623 DOI: 10.1016/0003-9861(85)90165-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Microsomal preparations from flax seedlings have recently been shown to convert L-valine to acetone cyanohydrin, the precursor of the cyanogenic glucoside linamarin [A. J. Cutler and E. E. Conn (1981) Arch. Biochem. Biophys. 212, 468-474]. Further details of this four-step biosynthetic sequence and also details of the analogous reactions in lotaustralin biosynthesis have been obtained. The lotaustralin precursor, 2-methylbutyraldoxime, is the best substrate for cyanide production (Vmax = 413 nmol h-1 g fresh wt-1) and inhibits the conversion of valine and isoleucine into products. Similarly, the linamarin precursor isobutyraldoxime is an excellent substrate (Vmax = 400 nmol h-1 g fresh wt-1) and also inhibits oxidation of the amino acids. The substrate specificity of the oxime-metabolizing step is low and a variety of aliphatic oximes are converted to cyanide. On the other hand, the activity of the microsomal extract is highly selective with regard to the amino acid substrate since, of the aliphatic amino acids tested, only valine and isoleucine are metabolized. We were unable to demonstrate product formation from isobutyronitrile (a linamarin precursor) but did observe detectable cyanide formation from 2-methylcyanobutane, the corresponding precursor of lotaustralin. Competition experiments showed that the biosynthesis of linamarin and lotaustralin is not likely to be catalyzed by separate enzyme systems.
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Hrazdina G, Wagner GJ. Metabolic pathways as enzyme complexes: evidence for the synthesis of phenylpropanoids and flavonoids on membrane associated enzyme complexes. Arch Biochem Biophys 1985; 237:88-100. [PMID: 3970546 DOI: 10.1016/0003-9861(85)90257-7] [Citation(s) in RCA: 101] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In earlier studies [G. Hrazdina, G. J. Wagner, and H. W. Siegelman (1978) Phytochemistry 17, 53-56; G. J. Wagner and G. Hrazdina (1984) Plant Physiol. 74, 901-906], evidence was obtained suggesting that the endoplasmic reticulum was a site for phenylpropanoid and flavonoid metabolism in petal tissue, and that (a) multienzyme complex(es) might be involved in this metabolism. Now, the possible role of membrane-bound multienzyme complexes in phenylpropanoid and flavonoid metabolism in three tissues has been investigated by (1) correlating enzyme induction kinetics and rates, (2) examining the molecular weight of putative complexes, (3) channeling of substrates, (4) determining the susceptibility of bound activities to trypsin digestion, and (5) investigating the structurally linked latency of bound activities. Results suggest that at least a part--and possibly the entire pathway--from phenylalanine to flavonoids is membrane (endoplasmic reticulum) associated, and that this metabolism is facilitated by a multienzyme complex. Phenylalanine ammonia lyase, the first enzyme of the biosynthetic sequence, and a flavonoid glucosyltransferase, the last, appear to be located in the lumen of the membranes. Cinnamate 4-hydroxylase is membrane embedded, while other enzyme activities appear to be weakly associated with the cytoplasmic face of endoplasmic reticulum membranes.
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Collinge DB, Hughes MA. Evidence that linamarin and lotaustralin, the two cyanogenic glucosides of Trifolium repens L., are synthesized by a single set of microsomal enzymes controlled by the Ac/ac locus. ACTA ACUST UNITED AC 1984. [DOI: 10.1016/0304-4211(84)90134-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Hösel W, Schiel O. Biosynthesis of cyanogenic glucosides: in vitro analysis of the glucosylation step. Arch Biochem Biophys 1984; 229:177-86. [PMID: 6230992 DOI: 10.1016/0003-9861(84)90142-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The last step in the biosynthesis of cyanogenic glucosides, the glucosylation of the cyanohydrin intermediate, has been investigated in detail using Triglochin maritima seedlings. The glucosyltransferase activity is not associated with membranes and appears to be a "soluble" enzyme. The cyanohydrin intermediate, which is formed by hydroxylation of 4-hydroxyphenylacetonitrile by a membrane-bound enzyme, is free to equilibrate in the presence of the glucosyltransferase and UDPG, because it can be trapped very efficiently. This indicates that this intermediate is not channeled (unlike some of the other intermediates), although it is probably the most labile of all of them. The glucosyltransferase of T. maritima responsible for the glucosylation of the cyanohydrin was separated from another glucosyltransferase, which used 4-hydroxybenzylalcohol as a substrate, and purified over 200-fold. It catalyzed the glucose transfer from UDPG to only 4-hydroxymandelonitrile and 3,4-dihydroxymandelonitrile, giving rise to the respective cyanogenic glucosides. Although the activities with these two substrates behaved differently in certain respects (e.g., extent of inactivation during purification and difference in activation by higher salt concentrations), most of the data acquired favor the view that only one enzyme in T. maritima is responsible for the glucosylation of both substrates.
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Collinge DB, Hughes MA. In vitro characterization of the Ac locus in white clover (Trifolium repens L.). Arch Biochem Biophys 1982; 218:38-45. [PMID: 7149740 DOI: 10.1016/0003-9861(82)90318-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
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