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Cai J, Jia R, Jiang Y, Fu J, Dong T, Deng J, Zhang L. Functional verification of the JmLFY gene associated with the flowering of Juglans mandshurica Maxim. PeerJ 2023; 11:e14938. [PMID: 36908820 PMCID: PMC10000305 DOI: 10.7717/peerj.14938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Accepted: 01/31/2023] [Indexed: 03/09/2023] Open
Abstract
In this study, a pBI121-JmLFY plant expression vector was constructed on the basis of obtaining the full-length sequence of the JmLFY gene from Juglans mandshurica, which was then used for genetic transformation via Agrobacterium inflorescence infection using wild-type Arabidopsis thaliana and lfy mutants as transgenic receptors. Seeds of positive A. thaliana plants with high expression of JmLFY were collected and sowed till the homozygous T3 regeneration plants were obtained. Then the expression of flowering-related genes (AtAP1, AtSOC1, AtFT and AtPI) in T3 generation plants were analyzed and the results showed that JmLFY gene overexpression promoted the expression of flowering-related genes and resulted in earlier flowering in A. thaliana. The A. thaliana plants of JmLFY-transformed and JmLFY-transformed lfy mutants appeared shorter leaves, longer fruit pods, and fewer cauline leaves than those of wild-type and the lfy mutants plants, respectively. In addition, some secondary branches in the transgenic plants converted into inflorescences, which indicated that the overexpression of JmLFY promoted the transition from vegetative growth to reproductive growth, and compensate the phenotypic defects of lfy mutant partially. The results provides a scientific reference for formulating reasonable genetic improvement strategies such as shortening childhood, improving yield and quality, and breeding desirable varieties, which have important guiding significance in production.
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Affiliation(s)
- Jiayou Cai
- Shenyang Agricultural University, Shenyang, Liaoning, China
- Key Laboratory of Forest Tree Genetics, Breeding and Cultivation of Liaoning Province, Shenyang, Liaoning, China
| | - Ruoxue Jia
- Shenyang Agricultural University, Shenyang, Liaoning, China
| | - Ying Jiang
- Shenyang Agricultural University, Shenyang, Liaoning, China
| | - Jingqi Fu
- Shenyang Agricultural University, Shenyang, Liaoning, China
- Key Laboratory of Forest Tree Genetics, Breeding and Cultivation of Liaoning Province, Shenyang, Liaoning, China
| | - Tianyi Dong
- Shenyang Agricultural University, Shenyang, Liaoning, China
- Key Laboratory of Forest Tree Genetics, Breeding and Cultivation of Liaoning Province, Shenyang, Liaoning, China
| | - Jifeng Deng
- Shenyang Agricultural University, Shenyang, Liaoning, China
- Key Laboratory of Forest Tree Genetics, Breeding and Cultivation of Liaoning Province, Shenyang, Liaoning, China
| | - Lijie Zhang
- Shenyang Agricultural University, Shenyang, Liaoning, China
- Key Laboratory of Forest Tree Genetics, Breeding and Cultivation of Liaoning Province, Shenyang, Liaoning, China
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Wang Z, He F, Mu Y, Zhang L, Liu Z, Liu D, Yang J, Jin Z, Pei Y. Identification and functional characterization of a cystathionine β-lyase (CBL) enzyme for H 2S production in Arabidopsis thaliana. PLANT PHYSIOLOGY AND BIOCHEMISTRY : PPB 2022; 182:76-89. [PMID: 35472754 DOI: 10.1016/j.plaphy.2022.04.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 04/02/2022] [Accepted: 04/05/2022] [Indexed: 06/14/2023]
Abstract
Sulfide or sulfur metabolism plays an important role in the growth and development of plants. Cystathionine β-lyase (CBL) is an important enzyme in methionine synthesis, but a comprehensive understanding of CBL functions is limited. As the third gasotransmitter, hydrogen sulfide (H2S) plays important physiological roles in plants. In this study, we found that the endogenous H2S content in Arabidopsis thaliana cbl mutants was lower than that in the wild type. Under PEG-based osmotic stress conditions, the H2S contents of CBL-overexpression (OE-CBL) plants increased significantly compared with the wild type. Additionally, the OE-CBL plants increased their tolerance to osmotic stress by increasing the transcription levels of drought-related genes and their relative water-loss rates. Compared with cbl and wild type, OE-CBL plants resisted drought stress by significantly closing their stomata, resulting in improved survival rates. Root tip-bending experiments showed that CBL overexpression relieved osmotic, heavy metal and cold stresses in Arabidopsis. The recombinant CBL activity in vitro revealed that CBL produced H2S using L-cysteine as a substrate. Thus, CBL had a very strong cysteine desulfhydrase activity that could produce endogenous H2S using L-cysteine as a substrate, and it played an important role in plant abiotic stress resistance.
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Affiliation(s)
- Zhiqing Wang
- School of Life Science and Shanxi Key Laboratory for Research and Development of Regional Plants, Shanxi University, Taiyuan, Shanxi Province, 030006, China
| | - Feng He
- School of Life Science and Shanxi Key Laboratory for Research and Development of Regional Plants, Shanxi University, Taiyuan, Shanxi Province, 030006, China; The Affiliated High School of Shanxi University, Taiyuan, Shanxi Province, 030006, China
| | - Yao Mu
- Institute of Space Information, Space Engineering University, Beijing, 101416, China
| | - Liping Zhang
- School of Life Science and Shanxi Key Laboratory for Research and Development of Regional Plants, Shanxi University, Taiyuan, Shanxi Province, 030006, China
| | - Zhiqiang Liu
- School of Life Science and Shanxi Key Laboratory for Research and Development of Regional Plants, Shanxi University, Taiyuan, Shanxi Province, 030006, China
| | - Danmei Liu
- School of Life Science and Shanxi Key Laboratory for Research and Development of Regional Plants, Shanxi University, Taiyuan, Shanxi Province, 030006, China
| | - Jinbao Yang
- Shenzhen Branch, Guangdong Laboratory of Lingnan Modern Agriculture, Genome Analysis Laboratory of the Ministry of Agriculture and Rural Affairs, Agricultural Genomics Institute at Shenzhen, Chinese Academy of Agricultural Sciences, Shenzhen, 518120, China
| | - Zhuping Jin
- School of Life Science and Shanxi Key Laboratory for Research and Development of Regional Plants, Shanxi University, Taiyuan, Shanxi Province, 030006, China.
| | - Yanxi Pei
- School of Life Science and Shanxi Key Laboratory for Research and Development of Regional Plants, Shanxi University, Taiyuan, Shanxi Province, 030006, China.
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Oogai S, Fukuta M, Watanabe K, Inafuku M, Oku H. Molecular characterization of mimosinase and cystathionine β-lyase in the Mimosoideae subfamily member Mimosa pudica. JOURNAL OF PLANT RESEARCH 2019; 132:667-680. [PMID: 31368041 DOI: 10.1007/s10265-019-01128-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 07/27/2019] [Indexed: 06/10/2023]
Abstract
Mimosinase degrades the non-protein amino acid mimosine and is thought to have evolved from cystathionine β-lyase (CBL) via gene duplication. However, no study has, to date, compared the molecular characteristics of mimosinase and CBL. We therefore cloned mimosinase and CBL from the Mimosoideae subfamily member Mimosa pudica (Mp) and explored the molecular relationship between mimosinase and CBL for the first time. The recombinant Mp mimosinase degraded both mimosine and cystathionine with a much higher turnover number (kcat) for mimosine compared with cystathionine, and Mp CBL utilized only cystathionine as a substrate. The critical residues implicated in the substrate binding of Arabidopsis thaliana CBL (Tyr-127, Arg-129, Tyr-181, and Arg-440) were highly conserved in both Mp mimosinase and CBL. However, homology modeling and molecular simulation of these enzymes predicted variations in the residues that interact with substrates. A mutation experiment on Mp mimosinase revealed that the disruption of a disulfide bond in the vicinity of the pyridoxal-5'-phosphate domain increased the enzyme's preference toward cystathionine. Treatment of Mp mimosinase with a disulfide-cleavage agent also decreased mimosinase activity. Furthermore, mutation near the conserved binding residue altered the substrate preference between mimosine and cystathionine. Molecular dynamics simulations of Mp mimosinase suggested a closer coordination of the residues that interact with mimosine at the active site compared with cystathionine, indicating a more compact pocket size for mimosine degradation. This study thus may provide new insights into the molecular diversification of CBL, a C-S lyase, into the C-N lyase mimosinase in the Mimosoideae subfamily.
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Affiliation(s)
- Shigeki Oogai
- The United Graduate School of Agricultural Sciences, Kagoshima University, 1-21-24, Ko-rimoto, Kagoshima, 890-8580, Japan
| | - Masakazu Fukuta
- The United Graduate School of Agricultural Sciences, Kagoshima University, 1-21-24, Ko-rimoto, Kagoshima, 890-8580, Japan
- Faculty of Agriculture, University of the Ryukyus, 1 Senbaru, Nishihara-cho, Nakagami-gun, Okinawa, 903-0213, Japan
| | - Keiichi Watanabe
- The United Graduate School of Agricultural Sciences, Kagoshima University, 1-21-24, Ko-rimoto, Kagoshima, 890-8580, Japan
- Faculty of Agriculture, Saga University, 1, Honjo-machi, Saga, 840-8502, Japan
| | - Masashi Inafuku
- Molecular Biotechnology Group, Center of Molecular Bioscience, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa, 903-0213, Japan
| | - Hirosuke Oku
- The United Graduate School of Agricultural Sciences, Kagoshima University, 1-21-24, Ko-rimoto, Kagoshima, 890-8580, Japan.
- Molecular Biotechnology Group, Center of Molecular Bioscience, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa, 903-0213, Japan.
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Jander G, Joshi V. Aspartate-Derived Amino Acid Biosynthesis in Arabidopsis thaliana. THE ARABIDOPSIS BOOK 2009; 7:e0121. [PMID: 22303247 PMCID: PMC3243338 DOI: 10.1199/tab.0121] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/19/2023]
Abstract
The aspartate-derived amino acid pathway in plants leads to the biosynthesis of lysine, methionine, threonine, and isoleucine. These four amino acids are essential in the diets of humans and other animals, but are present in growth-limiting quantities in some of the world's major food crops. Genetic and biochemical approaches have been used for the functional analysis of almost all Arabidopsis thaliana enzymes involved in aspartate-derived amino acid biosynthesis. The branch-point enzymes aspartate kinase, dihydrodipicolinate synthase, homoserine dehydrogenase, cystathionine gamma synthase, threonine synthase, and threonine deaminase contain well-studied sites for allosteric regulation by pathway products and other plant metabolites. In contrast, relatively little is known about the transcriptional regulation of amino acid biosynthesis and the mechanisms that are used to balance aspartate-derived amino acid biosynthesis with other plant metabolic needs. The aspartate-derived amino acid pathway provides excellent examples of basic research conducted with A. thaliana that has been used to improve the nutritional quality of crop plants, in particular to increase the accumulation of lysine in maize and methionine in potatoes.
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Affiliation(s)
- Georg Jander
- Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853 USA
- Address correspondence to
| | - Vijay Joshi
- Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853 USA
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Grossman A, Takahashi H. MACRONUTRIENT UTILIZATION BY PHOTOSYNTHETIC EUKARYOTES AND THE FABRIC OF INTERACTIONS. ANNUAL REVIEW OF PLANT PHYSIOLOGY AND PLANT MOLECULAR BIOLOGY 2001; 52:163-210. [PMID: 11337396 DOI: 10.1146/annurev.arplant.52.1.163] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Organisms acclimate to a continually fluctuating nutrient environment. Acclimation involves responses specific for the limiting nutrient as well as responses that are more general and occur when an organism experiences different stress conditions. Specific responses enable organisms to efficiently scavenge the limiting nutrient and may involve the induction of high-affinity transport systems and the synthesis of hydrolytic enzymes that facilitate the release of the nutrient from extracellular organic molecules or from internal reserves. General responses include changes in cell division rates and global alterations in metabolic activities. In photosynthetic organisms there must be precise regulation of photosynthetic activity since when severe nutrient limitation prevents continued cell growth, excitation of photosynthetic pigments could result in the formation of reactive oxygen species, which can severely damage structural and functional features of the cell. This review focuses on ways that photosynthetic eukaryotes assimilate the macronutrients nitrogen, sulfur, and phosphorus, and the mechanisms that govern assimilatory activities. Also discussed are molecular responses to macronutrient limitation and the elicitation of those responses through integration of environmental and cellular cues.
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Affiliation(s)
- Arthur Grossman
- Department of Plant Biology, The Carnegie Institution of Washington 260 Panama Street, Stanford, California 94305; e-mail: , RIKEN Plant Science Center, 2-l Hirosawa, Wako, Saitama, 351-0198, Japan; e-mail:
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Breitinger U, Clausen T, Ehlert S, Huber R, Laber B, Schmidt F, Pohl E, Messerschmidt A. The three-dimensional structure of cystathionine beta-lyase from Arabidopsis and its substrate specificity. PLANT PHYSIOLOGY 2001; 126:631-42. [PMID: 11402193 PMCID: PMC111155 DOI: 10.1104/pp.126.2.631] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2001] [Revised: 03/05/2001] [Accepted: 03/22/2001] [Indexed: 05/22/2023]
Abstract
The pyridoxal 5'-phosphate-dependent enzyme cystathionine beta-lyase (CBL) catalyzes the penultimate step in the de novo biosynthesis of Met in microbes and plants. Absence of CBL in higher organisms makes it an important target for the development of antibiotics and herbicides. The three-dimensional structure of cystathionine beta-lyase from Arabidopsis was determined by Patterson search techniques, using the structure of tobacco (Nicotiana tabacum) cystathionine gamma-synthase as starting point. At a resolution of 2.3 A, the model was refined to a final crystallographic R-factor of 24.9%. The overall structure is very similar to other pyridoxal 5'-phosphate-dependent enzymes of the gamma-family. Exchange of a few critical residues within the active site causes the different substrate preferences between Escherichia coli and Arabidopsis CBL. Loss of interactions at the alpha-carboxyl site is the reason for the poorer substrate binding of Arabidopsis CBL. In addition, the binding pocket of Arabidopsis CBL is larger than that of E. coli CBL, explaining the similar binding of L-cystathionine and L-djenkolate in Arabidopsis CBL in contrast to E. coli CBL, where the substrate binding site is optimized for the natural substrate cystathionine.
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Affiliation(s)
- U Breitinger
- Max-Planck-Institut für Biochemie, Abteilung Strukturforschung, Am Klopferspitz 18a, D-82152 Martinsried, Germany
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Gakière B, Ravanel S, Droux M, Douce R, Job D. Mechanisms to account for maintenance of the soluble methionine pool in transgenic Arabidopsis plants expressing antisense cystathionine gamma-synthase cDNA. COMPTES RENDUS DE L'ACADEMIE DES SCIENCES. SERIE III, SCIENCES DE LA VIE 2000; 323:841-51. [PMID: 11098400 DOI: 10.1016/s0764-4469(00)01242-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
To investigate the role of cystathionine gamma-synthase (CGS) in the regulation of methionine synthesis Arabidopsis plants were transformed with a full-length antisense CGS cDNA and transformants analysed. Plants that were heterozygous for the transgene showed a 20-fold reduction of CGS activity that was accompanied by severe growth retardation and morphological abnormalities, from germination to flowering. Application of exogenous methionine to the transgenic lines restored normal growth. Surprisingly, transformed Arabidopsis plants exhibited a modest decrease in methionine content (35% reduction of the wild-type level) but a seven-fold decrease in the soluble pool of S-methylmethionine (SMM), a compound that plays a major role in storage and transport of reduced sulphur and labile methyl moieties. Several mechanisms can account for the maintenance of the soluble pool of methionine. First, the observed 20-fold increase in O-phosphohomoserine, a substrate of CGS, could compensate for the depressed level of CGS polypeptide by increasing the net rate of catalysis supported by the remaining enzyme. Second, the transgenic plants exhibited a two-fold increased level of cystathionine beta-lyase, the second enzyme in the methionine biosynthetic pathway. This indicates that enzymes other than CGS are subjected to a regulatory control by methionine or one of its metabolites. In addition to these mechanisms affecting de novo methionine synthesis, the recruitment of SMM to produce methionine may account for the small change of methionine levels in transgenic lines.
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Affiliation(s)
- B Gakière
- Laboratoire mixte CNRS/Inra/Aventis (UMR 1932), Aventis CropScience, Pierre-Baizet, France
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Maimann S, Wagner C, Kreft O, Zeh M, Willmitzer L, Höfgen R, Hesse H. Transgenic potato plants reveal the indispensable role of cystathionine beta-lyase in plant growth and development. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2000; 23:747-758. [PMID: 10998186 DOI: 10.1046/j.1365-313x.2000.00842.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Methionine (Met) is an essential amino acid that is often unavailable at sufficient dietary levels. In order to better understand Met pathway regulation, a cDNA encoding cystathionine beta-lyase (CbL; EC 4.4.1.8) has been cloned from Solanum tuberosum. An antisense construct of this gene was used to generate transgenic potato plants with reduced CbL levels. Transgenic plants exhibiting leaf CbL activity levels of up to 50% below wild-type levels were obtained. Metabolite analysis revealed a reduction in Met levels in these CbL antisense plants, as well as remarkable increases in the pathway intermediates cystathionine, homoserine and cysteine. Unexpectedly, an increase in homocysteine was also observed. Levels of aspartate amino acid pathway intermediates (including aspartate, lysine and threonine) remained essentially unaffected. Neither transcript levels nor protein products of other pathway-relevant genes were altered significantly in these plants. CbL antisense plants exhibited an altered phenotype characterized by a bushy growth habit, small light-green leaves and small tubers. This phenotype could be alleviated upon Met supplementation, suggesting that low Met levels, rather than pathway intermediate accumulation, is responsible for the phenotypic effects of CbL transgene expression. These data unequivocally demonstrate the central role of CbL in Met biosynthesis, and, subsequently, in plant growth and development.
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Affiliation(s)
- S Maimann
- Max-Planck-Institut für Molekulare Pflanzenphysiologie, Am Mühlenberg 1, 14476 Golm, Germany
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Ravanel S, Gakière B, Job D, Douce R. The specific features of methionine biosynthesis and metabolism in plants. Proc Natl Acad Sci U S A 1998; 95:7805-12. [PMID: 9636232 PMCID: PMC22764 DOI: 10.1073/pnas.95.13.7805] [Citation(s) in RCA: 423] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Plants, unlike other higher eukaryotes, possess all the necessary enzymatic equipment for de novo synthesis of methionine, an amino acid that supports additional roles than simply serving as a building block for protein synthesis. This is because methionine is the immediate precursor of S-adenosylmethionine (AdoMet), which plays numerous roles of being the major methyl-group donor in transmethylation reactions and an intermediate in the biosynthesis of polyamines and of the phytohormone ethylene. In addition, AdoMet has regulatory function in plants behaving as an allosteric activator of threonine synthase. Among the AdoMet-dependent reactions occurring in plants, methylation of cytosine residues in DNA has raised recent interest because impediment of this function alters plant morphology and induces homeotic alterations in flower organs. Also, AdoMet metabolism seems somehow implicated in plant growth via an as yet fully understood link with plant-growth hormones such as cytokinins and auxin and in plant pathogen interactions. Because of this central role in cellular metabolism, a precise knowledge of the biosynthetic pathways that are responsible for homeostatic regulation of methionine and AdoMet in plants has practical implications, particularly in herbicide design.
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Affiliation(s)
- S Ravanel
- Laboratoire mixte Centre National de la Recherche Scientifique/Rhône-Poulenc (UMR041), Rhône-Poulenc Agrochimie, 14-20 rue Pierre Baizet, 69263, Lyon cedex 9, France
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Azevedo RA, Arruda P, Turner WL, Lea PJ. The biosynthesis and metabolism of the aspartate derived amino acids in higher plants. PHYTOCHEMISTRY 1997; 46:395-419. [PMID: 9332022 DOI: 10.1016/s0031-9422(97)00319-1] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The essential amino acids lysine, threonine, methionine and isoleucine are synthesised in higher plants via a common pathway starting with aspartate. The regulation of the pathway is discussed in detail, and the properties of the key enzymes described. Recent data obtained from studies of regulation at the gene level and information derived from mutant and transgenic plants are also discussed. The herbicide target enzyme acetohydroxyacid synthase involved in the synthesis of the branched chain amino acids is reviewed.
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Affiliation(s)
- R A Azevedo
- Departamento de Genética, Universidade de São Paulo, Piracicaba, SP, Brasil
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Ravanel S. Methionine biosynthesis in higher plants: biochemical and molecular characterization of the transsulfuration pathway enzymes. ACTA ACUST UNITED AC 1997. [DOI: 10.1016/s0764-4469(97)81977-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Ravanel S, Job D, Douce R. Purification and properties of cystathionine beta-lyase from Arabidopsis thaliana overexpressed in Escherichia coli. Biochem J 1996; 320 ( Pt 2):383-92. [PMID: 8973544 PMCID: PMC1217943 DOI: 10.1042/bj3200383] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Cystathionine beta-lyase is a key enzyme in sulphur metabolism that catalyses the second reaction specific for methionine biosynthesis, the pyridoxal 5'-phosphate-dependent beta-cleavage of cystathionine to produce homocysteine. To obtain insight into the biochemical properties of the plant enzyme, the cDNA encoding cystathionine beta-lyase from Arabidopsis thaliana was used to construct an overproducing Escherichia coli strain. The recombinant enzyme was isolated at high yield (29 mg of pure protein/litre of cell culture) using an efficient two-step purification procedure. Physicochemical properties of the Arabidopsis cystathionine beta-lyase were similar to those previously reported for the bacterial enzymes. In particular, the native recombinant protein is a tetramer composed of four identical subunits of 46 kDa, each being associated with one molecule of pyridoxal 5'-phosphate. Interaction between the apoenzyme and pyridoxal 5'-phosphate is extremely tight, being characterized by a Kd value of 0.5 microM. Purification and sequencing of the phosphopyridoxyl peptide established that Schiff base formation between the cofactor and the holoenzyme occurs at lysine-278. The substrate specificity of the recombinant cystathionine beta-lyase resembles that of the enzyme isolated from other sources, cystathionine and djenkolate being the most effective substrates. The cystathionine analogue aminoethoxyvinylglycine irreversibly inactivates the recombinant cystathionine beta-lyase. The inactivation is accompanied by dramatic modification of the spectral properties of the enzyme that can be attributed to the attack of the azomethine linkage between pyridoxal 5'-phosphate and lysine-278 of the polypeptide by aminoethoxyvinylglycine.
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Affiliation(s)
- S Ravanel
- Laboratoire Mixte CNRS/Rhône-Poulenc (UMR41), Rhône-Poulenc Agrochimie, Lyon, France
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