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Schenck CA, Westphal J, Jayaraman D, Garcia K, Wen J, Mysore KS, Ané J, Sumner LW, Maeda HA. Role of cytosolic, tyrosine-insensitive prephenate dehydrogenase in Medicago truncatula. PLANT DIRECT 2020; 4:e00218. [PMID: 32368714 PMCID: PMC7196213 DOI: 10.1002/pld3.218] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2019] [Revised: 03/21/2020] [Accepted: 03/25/2020] [Indexed: 05/26/2023]
Abstract
l-Tyrosine (Tyr) is an aromatic amino acid synthesized de novo in plants and microbes downstream of the shikimate pathway. In plants, Tyr and a Tyr pathway intermediate, 4-hydroxyphenylpyruvate (HPP), are precursors to numerous specialized metabolites, which are crucial for plant and human health. Tyr is synthesized in the plastids by a TyrA family enzyme, arogenate dehydrogenase (ADH/TyrAa), which is feedback inhibited by Tyr. Additionally, many legumes possess prephenate dehydrogenases (PDH/TyrAp), which are insensitive to Tyr and localized to the cytosol. Yet the role of PDH enzymes in legumes is currently unknown. This study isolated and characterized Tnt1-transposon mutants of MtPDH1 (pdh1) in Medicago truncatula to investigate PDH function. The pdh1 mutants lacked PDH transcript and PDH activity, and displayed little aberrant morphological phenotypes under standard growth conditions, providing genetic evidence that MtPDH1 is responsible for the PDH activity detected in M. truncatula. Though plant PDH enzymes and activity have been specifically found in legumes, nodule number and nitrogenase activity of pdh1 mutants were not significantly reduced compared with wild-type (Wt) during symbiosis with nitrogen-fixing bacteria. Although Tyr levels were not significantly different between Wt and mutants under standard conditions, when carbon flux was increased by shikimate precursor feeding, mutants accumulated significantly less Tyr than Wt. These data suggest that MtPDH1 is involved in Tyr biosynthesis when the shikimate pathway is stimulated and possibly linked to unidentified legume-specific specialized metabolism.
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Affiliation(s)
- Craig A. Schenck
- Department of BotanyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Present address:
Department of Biochemistry and Molecular BiologyMichigan State UniversityEast LansingMIUSA
| | - Josh Westphal
- Department of BotanyUniversity of Wisconsin‐MadisonMadisonWIUSA
| | | | - Kevin Garcia
- Department of BacteriologyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Department of Crop and Soil SciencesNorth Carolina State UniversityRaleighNCUSA
| | | | | | - Jean‐Michel Ané
- Department of BacteriologyUniversity of Wisconsin‐MadisonMadisonWIUSA
- Department of AgronomyUniversity of Wisconsin‐MadisonMadisonWIUSA
| | - Lloyd W. Sumner
- Department of BiochemistryUniversity of MissouriColumbiaMOUSA
- Metabolomics and Bond Life Sciences CentersUniversity of MissouriColumbiaMOUSA
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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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3
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Evolution of allosteric regulation in chorismate mutases from early plants. Biochem J 2017; 474:3705-3717. [DOI: 10.1042/bcj20170549] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 09/25/2017] [Accepted: 09/26/2017] [Indexed: 11/17/2022]
Abstract
Plants, fungi, and bacteria synthesize the aromatic amino acids: l-phenylalanine, l-tyrosine, and l-tryptophan. Chorismate mutase catalyzes the branch point reaction of phenylalanine and tyrosine biosynthesis to generate prephenate. In Arabidopsis thaliana, there are two plastid-localized chorismate mutases that are allosterically regulated (AtCM1 and AtCM3) and one cytosolic isoform (AtCM2) that is unregulated. Previous analysis of plant chorismate mutases suggested that the enzymes from early plants (i.e. bryophytes/moss, lycophytes, and basal angiosperms) formed a clade distinct from the isoforms found in flowering plants; however, no biochemical information on these enzymes is available. To understand the evolution of allosteric regulation in plant chorismate mutases, we analyzed a basal lineage of plant enzymes homologous to AtCM1 based on sequence similarity. The chorismate mutases from the moss/bryophyte Physcomitrella patens (PpCM1 and PpCM2), the lycophyte Selaginella moellendorffii (SmCM), and the basal angiosperm Amborella trichopoda (AmtCM1 and AmtCM2) were characterized biochemically. Tryptophan was a positive effector for each of the five enzymes examined. Histidine was a weak positive effector for PpCM1 and AmtCM1. Neither tyrosine nor phenylalanine altered the activity of SmCM; however, tyrosine was a negative regulator of the other four enzymes. Phenylalanine down-regulates both moss enzymes and AmtCM2. The 2.0 Å X-ray crystal structure of PpCM1 in complex with the tryptophan identified the allosteric effector site and reveals structural differences between the R- (more active) and T-state (less active) forms of plant chorismate mutases. Molecular insight into the basal plant chorismate mutases guides our understanding of the evolution of allosteric regulation in these enzymes.
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Westfall CS, Xu A, Jez JM. Structural evolution of differential amino acid effector regulation in plant chorismate mutases. J Biol Chem 2014; 289:28619-28. [PMID: 25160622 DOI: 10.1074/jbc.m114.591123] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Chorismate mutase converts chorismate into prephenate for aromatic amino acid biosynthesis. To understand the molecular basis of allosteric regulation in the plant chorismate mutases, we analyzed the three Arabidopsis thaliana chorismate mutase isoforms (AtCM1-3) and determined the x-ray crystal structures of AtCM1 in complex with phenylalanine and tyrosine. Functional analyses show a wider range of effector control in the Arabidopsis chorismate mutases than previously reported. AtCM1 is activated by tryptophan with phenylalanine and tyrosine acting as negative effectors; however, tryptophan, cysteine, and histidine activate AtCM3. AtCM2 is a nonallosteric form. The crystal structure of AtCM1 in complex with tyrosine and phenylalanine identifies differences in the effector sites of the allosterically regulated yeast enzyme and the other two Arabidopsis isoforms. Site-directed mutagenesis of residues in the effector site reveals key features leading to differential effector regulation in these enzymes. In AtCM1, mutations of Gly-213 abolish allosteric regulation, as observed in AtCM2. A second effector site position, Gly-149 in AtCM1 and Asp-132 in AtCM3, controls amino acid effector specificity in AtCM1 and AtCM3. Comparisons of chorismate mutases from multiple plants suggest that subtle differences in the effector site are conserved in different lineages and may lead to specialized regulation of this branch point enzyme.
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Affiliation(s)
- Corey S Westfall
- From the Department of Biology, Washington University, St. Louis, Missouri 63130
| | - Ang Xu
- From the Department of Biology, Washington University, St. Louis, Missouri 63130
| | - Joseph M Jez
- From the Department of Biology, Washington University, St. Louis, Missouri 63130
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5
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Seasonal clonal variations and effects of stresses on quality chemicals and prephenate dehydratase enzyme activity in tea (Camellia sinensis). Eur Food Res Technol 2010. [DOI: 10.1007/s00217-010-1379-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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6
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Hertel SC, Hieke M, Gröuger D. Purification and characterization of chorismate mutase isoenzymes from ruta graveolens l. ACTA ACUST UNITED AC 2004. [DOI: 10.1002/abio.370110113] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Mobley EM, Kunkel BN, Keith B. Identification, characterization and comparative analysis of a novel chorismate mutase gene in Arabidopsis thaliana. Gene 1999; 240:115-23. [PMID: 10564818 DOI: 10.1016/s0378-1119(99)00423-0] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Phenylalanine, tyrosine, and tryptophan have a dual biosynthetic role in plants; they are required for protein synthesis and are also precursors to a number of aromatic secondary metabolites critical to normal development and stress responses. Whereas much has been learned in recent years about the genetic control of tryptophan biosynthesis in Arabidopsis and other plants, relatively little is known about the genetic regulation of phenylalanine and tyrosine synthesis. We have isolated, characterized and determined the expression of Arabidopsis thaliana genes encoding chorismate mutase, the enzyme catalyzing the first committed step in phenylalanine and tyrosine synthesis. Three independent Arabidopsis chorismate mutase cDNAs were isolated by functional complementation of a Saccharomyces cerevisiae mutation. Two of these cDNAs have been reported independently (Eberhard et al., 1993. FEBS 334, 233-236; Eberhard et al., 1996. Plant J. 10, 815-821), but the third (designated CM-3) represents a novel gene. The different organ-specific expression patterns of these cDNAs, their regulation in response to pathogen infiltration, as well as the different enzymatic characteristics of the proteins they encode are also described. Together, these data suggest that each isoform may play a distinct physiological role in coordinating chorismate mutase activity with developmental and environmental signals.
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MESH Headings
- Amino Acid Sequence
- Amino Acids, Cyclic/pharmacology
- Arabidopsis/enzymology
- Arabidopsis/genetics
- Blotting, Northern
- Chorismate Mutase/drug effects
- Chorismate Mutase/genetics
- Chorismate Mutase/metabolism
- DNA, Complementary/chemistry
- DNA, Complementary/genetics
- DNA, Complementary/isolation & purification
- Gene Expression Regulation, Enzymologic
- Gene Expression Regulation, Plant
- Genes, Plant/genetics
- Genetic Complementation Test
- Isoenzymes/drug effects
- Isoenzymes/genetics
- Isoenzymes/metabolism
- Kinetics
- Molecular Sequence Data
- Mutation
- RNA, Plant/genetics
- RNA, Plant/metabolism
- Saccharomyces cerevisiae/genetics
- Sequence Alignment
- Sequence Analysis, DNA
- Sequence Homology, Amino Acid
- Tissue Distribution
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Affiliation(s)
- E M Mobley
- Department of Biochemistry, University of Chicago, Chicago, IL, USA
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8
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Verpoorte R, van der Heijden R, Moreno PR. Chapter 3 Biosynthesis of Terpenoid Indole Alkaloids in Catharanthus roseus Cells. THE ALKALOIDS: CHEMISTRY AND PHARMACOLOGY 1997. [DOI: 10.1016/s0099-9598(08)60017-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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9
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Romero R, Roberts M, Phillipson J. Chorismate mutase in microorganisms and plants. PHYTOCHEMISTRY 1995; 40:1015-1025. [PMID: 0 DOI: 10.1016/0031-9422(95)00408-y] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
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10
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Affiliation(s)
- R Bentley
- Department of Chemistry, University of Sheffield, U.K
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11
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Sing BK, Stidham MA, Shaner DL. Separation and characterization of two forms of acetohydroxy acid synthase from black mexican sweet corn cells. J Chromatogr A 1988. [DOI: 10.1016/s0021-9673(01)94028-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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12
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Kuroki GW, Conn EE. Purification and characterization of an inducible aromatic amino acid-sensitive form of chorismate mutase from Solanum tuberosum L. tubers. Arch Biochem Biophys 1988; 260:616-21. [PMID: 3341760 DOI: 10.1016/0003-9861(88)90489-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
An amino acid-sensitive form of chorismate mutase (CM) has been purified over 1000-fold from disks excised from tubers of Solanum tuberosum L. cv White Rose. Purification was accomplished by chromatography on Matrix Blue A followed by affinity chromatography with tryptophan as ligand. CM assays performed in the absence of tryptophan yielded pH-dependent sigmoidal kinetics. At pH 8.0, sigmoidal kinetics were observed with a Hill coefficient of 1.66 (S0.5 = 188 microM). However, a shift from sigmoidal to hyperbolic kinetics was observed when assays were performed at pH 8.5. Addition of 9 microM tryptophan to the assay resulted in maximum activation of the enzyme with a Ka of 1.2 microM. When assayed in the presence of tryptophan, hyperbolic kinetics were observed over the pH range 6.0-8.0. Addition of tryptophan also decreased the Km for chorismate from 185 to 45 microM. Tryptophan (0.1 mM) completely protected CM from inhibition by phenylalanine (1.8 mM) and tyrosine (1.8 mM). However, in the absence of the activator, phenylalanine and tyrosine exhibited 50% inhibition at 0.80 and 0.68 mM concentrations, respectively. Both phenylalanine and tyrosine competitively inhibited CM activity with Ki values of 550 and 440 mM, respectively. Arogenate (1.0 mM) had no effect on CM activity in either the presence or absence of tryptophan. Analytical isoelectric focusing yielded an isoelectric point of 4.73.
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Affiliation(s)
- G W Kuroki
- Department of Biochemistry and Biophysics, University of California, Davis 95616
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13
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[54] Chorismate mutase from mung bean and sorghum. Methods Enzymol 1987. [DOI: 10.1016/s0076-6879(87)42056-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
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14
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Smart CC, Amrhein N. Ultrastructural localisation by protein A-gold immunocytochemistry of 5-enolpyruvylshikimic acid 3-phosphate synthase in a plant cell culture which overproduces the enzyme. PLANTA 1987; 170:1-6. [PMID: 24232834 DOI: 10.1007/bf00392373] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/1986] [Accepted: 08/27/1986] [Indexed: 06/02/2023]
Abstract
Recently we have shown that cultured cells of the higher plant Corydalis sempervirens Pers., adapted to growth in the presence of high concentrations of the herbicide glyphosate, a potent specific inhibitor of the shikimate pathway enzyme 5-enolpyruvylshikimic acid 3-phosphate (EPSP) synthase (EC 2.5.1.19, 3-phosphoshikimate 1-carboxyvinyltransferase) oversynthesize the EPSP synthase protein (Smart et al., 1985, J. Biol. Chem. 260, 16338-16346). We now report that the EPSP synthase protein can be detected in cells of the adapted as well as of the non-adapted strain by the use of protein A-colloidal gold immunocytochemistry. The overproduced EPSP synthase in the glyphosate-adapted cells is located exclusively in the plastid and we find no evidence for the existence of extra-plastidic EPSP synthase in either strain.
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Affiliation(s)
- C C Smart
- Lehrstuhl für Pflanzenphysiologie, Ruhr-Universität Bochum, D-4630, Bochum, Federal Republic of Germany
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15
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Singh BK, Connelly JA, Conn EE. Chorismate mutase isoenzymes from Sorghum bicolor: purification and properties. Arch Biochem Biophys 1985; 243:374-84. [PMID: 4083892 DOI: 10.1016/0003-9861(85)90514-4] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Two forms of chorismate mutase (EC 5.4.99.5), designated as CM-1 and CM-2, have been detected in etiolated seedlings of Sorghum bicolor after DEAE-cellulose chromatography. CM-1 and CM-2 contained 44 and 56%, respectively, of the total activity measured after DEAE-cellulose chromatography. CM-1 was activated by tryptophan and inhibited by phenylalanine and tyrosine. In contrast, CM-2 was insensitive to all three aromatic amino acids. CM-1 and CM-2 were purified 1389- and 1018-fold, respectively, by anion exchange, hydrophobic, and dye matrix chromatography. The molecular weights estimated by gel filtration on Sephacryl S-200 were 56,000 for CM-1 and 48,000 for CM-2. Subunit molecular weights of the two forms were estimated by sodium dodecyl sulfate-gel electrophoresis at 36,000 and 51,000 for CM-1 and CM-2, respectively. Tryptophan was required for the stability of CM-1 at all stages of purification. Both isoenzymes were stable at 0 or -20 degrees C and had broad pH optima (6-10 for CM-1 and 7.5-9.5 for CM-2).
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16
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Bonner CA, Jensen RA. Novel features of prephenate aminotransferase from cell cultures of Nicotiana silvestris. Arch Biochem Biophys 1985; 238:237-46. [PMID: 3985619 DOI: 10.1016/0003-9861(85)90161-4] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A prephenate aminotransferase enzyme that produces L-arogenate was demonstrated in extracts from cultured-cell populations of Nicotiana silvestris. The enzyme was very active with low concentrations of prephenate, but required high concentrations of phenylpyruvate or 4-hydroxyphenylpyruvate to produce activity levels that were detectable. It is the most specific prephenate aminotransferase described to date from any source. Only L-glutamate and L-aspartate were effective amino-donor substrates. Prephenate concentrations greater than 1 mM produced substrate inhibition, an effect antagonized by increasing concentrations of L-glutamate cosubstrate. The enzyme was stable to storage for at least a month in the presence of pyridoxal 5'-phosphate, EDTA, and glycerol, and exhibited an unusually high temperature optimum of 70 degrees C. The identity of L-arogenate formed during catalysis was verified by high-performance liquid chromatography. DEAE-cellulose chromatography revealed two aromatic aminotransferase activities that were distinct from prephenate aminotransferase and which did not require the three protectants for stability. The aromatic aminotransferases were active with phenylpyruvate or 4-hydroxyphenylpyruvate as substrates, but not with prephenate. Both of the latter enzymes were similar in substrate specificity, and each exhibited a temperature optimum of 50 degrees C for catalysis. The primary in vivo function of the two aromatic aminotransferases is probably to transaminate between the aspartate/2-ketoglutarate and glutamate/oxaloacetate couples, since activities with the latter substrate combinations were an order of magnitude greater than with aromatic substrates. The demonstrated existence of a specific prephenate aminotransferase in N. silvestris meshes with other evidence supporting an important role for L-arogenate in tyrosine and phenylalanine biosynthesis in higher plants.
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Goers SK, Jensen RA. The differential allosteric regulation of two chorismate-mutase isoenzymes of Nicotiana silvestris. PLANTA 1984; 162:117-24. [PMID: 24254045 DOI: 10.1007/bf00410207] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/07/1983] [Accepted: 04/24/1984] [Indexed: 05/11/2023]
Abstract
The reaction catalyzed by chorismate mutase (EC 5.4.99.5) is a crucial step for biosynthesis of two aromatic amino acids as well as for the synthesis of phenylpropanoid compounds. The regulatory properties of two chorismate-mutase isoenzymes expressed in Nicotiana silvestris Speg. et Comes are consistent with their differential roles in pathway flow routes ending with L-phenylalanine and L-tyrosine on one hand (isoenzyme CM-1), and ending with secondary metabolites on the other hand (isoenzyme CM-2). Isoenzyme CM-1 was very sensitive to allosteric control by all three aromatic amino acids. At pH 6.1, L-tryptophan was a potent allosteric activator (K a =1.5 μM), while feedback inhibition was effected by L-tyrosine (K i =15 μM) or by L-phenylalanine (Ki=15 μM). At pH 6.1, all three effectors acted competitively, influencing the apparent K m for chorismate. All three allosteric effectors protected isoenzyme CM-1 at pH 6.1 from thermal inactivation at 52° C. L-Tryptophan abolished the weak positive cooperativity of substrate binding found with isoenzyme CM-1 only at low pH. At pH 7.2, the allosteric effects of L-tyrosine and L-tryptophan were only modestly different, in striking contrast to results obtained with L-phenylalanine. At pH 7.2 (i) the K i for L-phenylalanine was elevated over 30-fold to 500 μM, (ii) the kinetics of inhibition became non-competitive, and (iii) L-phenylalanine now failed to protect isoenzyme CM-1 against thermal inactivation. L-Phenylalanine may act at different binding sites depending upon the intracellular pH milieu. In-vitro data indicated that the relative ability of allosteric activation to dominate over allosteric inhibition increases markedly with both pH and temperature. The second isoenzyme, CM-2, was inhibited competitively by caffeic acid (K i =0.2 mM). Aromatic amino acids failed to affect CM-2 activity over a broad range of pH and temperature. Inhibition curves obtained in the presence of caffeic acid were sigmoid, yielding an interaction coefficient (from Hill plots) of n'=1.8.
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Affiliation(s)
- S K Goers
- Center for Somatic cell Genetics and Biochemistry, Department of Biological Sciences, State University of New York, 13901, Binghamton, NY, USA
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d'Amato TA, Ganson RJ, Gaines CG, Jensen RA. Subcellular localization of chorismate-mutase isoenzymes in protoplasts from mesophyll and suspension-cultured cells of Nicotiana silvestris. PLANTA 1984; 162:104-108. [PMID: 24254043 DOI: 10.1007/bf00410205] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/16/1984] [Accepted: 04/24/1984] [Indexed: 05/28/2023]
Abstract
The subcellular locations of two readily discriminated chorismate-mutase (EC 5.4.99.5) isoenzymes from Nicotiana silvestris Speg. et Comes were determined in protoplasts prepared from both leaf tissue and isogenic suspension-cultured cells. Differential centrifugation was used to obtain fractions containing plastids, a mixture of mitochondria and microbodies, and soluble cytosolic proteins. Isoenzyme CM-1 is sensitive to feedback inhibition by L-tyrosine and comprises the major fraction of total chorismate mutase in suspension-cultured cells. Isoenzyme CM-2 is not inhibited by L-tyrosine and its expression is maximal in organismal (leaf) tissue. Isoenzyme CM-1 is located in the plastid compartment since (i) proplastids contained more CM-1 activity than chloroplasts, (ii) both chloroplast and proplastid fractions possessed the tyrosine-sensitive isoenzyme, and (iii) latency determinations on washed chloroplast preparations confirmed the internal location of a tyrosine-sensitive isoenzyme. Isoenzyme CM-2 is located in the cytosol since (i) the supernatant fractions were heavily enriched for the tyrosineinsensitive activity, and (ii) a relatively greater amount of tyrosine-insensitive enzyme was present in the supernatant fraction derived from organismal tissue.
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Affiliation(s)
- T A d'Amato
- Center for Somatic-cell Genetics and Biochemistry, Department of Biological Sciences, State University of New York, 13901, Binghamton, NY, USA
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