Plant Methionine Synthase: New Insights into Properties and Expression
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C. Eckermann
Abstract
We investigated the enzyme methionine synthase (MSY) in Catharanthus roseus. The properties were characterized with purified protein isolated either from plant cell cultures or after heterologous expression in Escherichia coli. The protein was a monomer and accepted both the triglutamate (CH3-H4PteGlu3, apparent Km = 80μM) and the monoglutamate (CH3-H4PteGlu1, apparent Km = 350μM) of methyl-5,6,7,8- tetrahydropteroate as methyl donor, with a ratio of approximately 90 :1 in favor of the triglutamate. Both activities required inorganic phosphate, but with different kinetics, and both were dependent on reducing agents. The activity required zinc, as shown by depletion and reconstitution experiments. Mg2+ had no effect on the activity. Two MSY isoforms purified from parsley cell cultures revealed the same properties as the C. roseus enzyme, however, the parsley proteins had no detectable activity with the monoglutamate substrate. The second part of the work compared the expression of the three enzymes of the methyl cycle (MSY, S-adenosyl-L-methionine synthetase, S-adenosyl- L-homocysteine hydrolase). In cell cultures, all three enzymes were present under all conditions investigated, with small changes at the protein level and more pronounced changes at the RNA level. Studies with seedlings revealed a low expression of all three enzymes in cotyledons, when compared to hypocotyls and radiculas. Immunohistochemical experiments indicated that MSY expression in cotyledons is cell-type specific, with the strongest signals detected in the upper epidermis.
Copyright © 2000 by Walter de Gruyter GmbH & Co. KG
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- Two Differentially Regulated Class II Chitinases from Parsley
- IAA-Synthase, an Enzyme Complex from Arabidopsis thaliana Catalyzing the Formation of Indole-3-Acetic Acid from (S)-Tryptophan
- Topology Studies of the Chloroplast Protein Import Channel Toc75
- Plant Methionine Synthase: New Insights into Properties and Expression
- The Hepta-? -Glucoside Elicitor-Binding Proteins from Legumes Represent a Putative Receptor Family
- Octadecanoid and Jasmonate Signaling in Tomato (Lycopersicon esculentum Mill.) Leaves: Endogenous Jasmonates Do Not Induce Jasmonate Biosynthesis
- Metabolic Activity Decreases as an Adaptive Response to Low Internal Oxygen in Growing Potato Tubers
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- Identification of the Arabidopsis thaliana Flavonoid 3'-Hydroxylase Gene and Functional Expression of the Encoded P450 Enzyme
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- Non-Specific Depurination Activity of Saporin-S6, a Ribosome-Inactivating Protein, under Acidic Conditions
- Molecular Evolution in the Hypervariable Regions of Fetuin: Comparison between Human and African Green Monkey Fetuin
Articles in the same Issue
- To Our Authors, Readers and Subscribers
- Highlight: Plant Biological Chemistry
- The Structural Properties of Plant Peroxisomes and Their Metabolic Significance
- Active Oxygen Species as Mediators of Plant Immunity: Three Case Studies
- Post-Transcriptional Regulation of Phenylalanine Ammonia-Lyase Expression in Tobacco Following Recovery from Gene Silencing
- Two Differentially Regulated Class II Chitinases from Parsley
- IAA-Synthase, an Enzyme Complex from Arabidopsis thaliana Catalyzing the Formation of Indole-3-Acetic Acid from (S)-Tryptophan
- Topology Studies of the Chloroplast Protein Import Channel Toc75
- Plant Methionine Synthase: New Insights into Properties and Expression
- The Hepta-? -Glucoside Elicitor-Binding Proteins from Legumes Represent a Putative Receptor Family
- Octadecanoid and Jasmonate Signaling in Tomato (Lycopersicon esculentum Mill.) Leaves: Endogenous Jasmonates Do Not Induce Jasmonate Biosynthesis
- Metabolic Activity Decreases as an Adaptive Response to Low Internal Oxygen in Growing Potato Tubers
- Structure-Activity Relationships of Synthetic Analogs of Jasmonic Acid and Coronatine on Induction of Benzophenanthridine Alkaloid Accumulation in Eschscholzia californica Cell Cultures
- Identification of the Arabidopsis thaliana Flavonoid 3'-Hydroxylase Gene and Functional Expression of the Encoded P450 Enzyme
- Gut Bacteria May Be Involved in Interactions between Plants, Herbivores and Their Predators: Microbial Biosynthesis of N-Acylglutamine Surfactants as Elicitors of Plant Volatiles
- Different Signaling Pathways Are Involved in CCKB Receptor-Mediated MAP Kinase Activation in COS-7 Cells
- Non-Specific Depurination Activity of Saporin-S6, a Ribosome-Inactivating Protein, under Acidic Conditions
- Molecular Evolution in the Hypervariable Regions of Fetuin: Comparison between Human and African Green Monkey Fetuin
