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Edwards MC, Liepman AH. Spectrophotometric Assays for Measuring Photorespiratory Glutamate:Glyoxylate and Serine:Glyoxylate Aminotransferase Reactions. Methods Mol Biol 2024; 2792:41-49. [PMID: 38861077 DOI: 10.1007/978-1-0716-3802-6_4] [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] [Indexed: 06/12/2024]
Abstract
Glutamate:glyoxylate aminotransferase (GGAT; EC 2.6.1.4) and serine:glyoxylate aminotransferase activities (SGAT; EC 2.6.1.45) are central photorespiratory reactions within plant peroxisomes. Both enzymatic reactions convert glyoxylate, a product of glycolate oxidase, to glycine, a substrate of the mitochondrial glycine decarboxylase complex. The GGAT reaction uses glutamate as an amino group donor and also produces α-ketoglutarate, which is recycled to glutamate in plastids by ferredoxin-dependent glutamate synthase. Using serine, a product of mitochondrial serine hydroxymethyltransferase, as an amino group donor, the SGAT reaction also produces hydroxypyruvate, a substrate of hydroxypyruvate reductase. The activities of these photorespiratory aminotransferases can be measured using indirect, coupled, spectrophotometric assays, detailed herein.
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Affiliation(s)
- Mair C Edwards
- Biology Department, Eastern Michigan University, Ypsilanti, MI, USA
| | - Aaron H Liepman
- Biology Department, Eastern Michigan University, Ypsilanti, MI, USA.
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Duminil P, Oury C, Hodges M, Glab N. Determination of Phosphoglycolate Phosphatase Activity via a Coupled Reaction Using Recombinant Glycolate Oxidase. Methods Mol Biol 2024; 2792:29-39. [PMID: 38861076 DOI: 10.1007/978-1-0716-3802-6_3] [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] [Indexed: 06/12/2024]
Abstract
Phosphoglycolate phosphatase (PGLP) dephosphorylates 2-phosphoglycolate to glycolate that can be further metabolized to glyoxylate by glycolate oxidase (GOX) via an oxidative reaction that uses O2 and releases H2O2. The oxidation of o-dianisidine by H2O2 catalyzed by a peroxidase can be followed in real time by an absorbance change at 440 nm. Based on these reactions, a spectrophotometric method for measuring PGLP activity using a coupled reaction with recombinant Arabidopsis thaliana GOX is described. This protocol has been used successfully with either purified PGLP or total soluble proteins extracted from Arabidopsis rosette leaves.
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Affiliation(s)
- Pauline Duminil
- Université Paris-Saclay, CNRS, INRAe, Université Paris Cité, Université d'Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Gif-sur-Yvette, France
- Department of Plant Biochemistry, Albrecht-von-Haller Institute for Plant Sciences, University of Gottingen, Gottingen, Germany
| | - Céline Oury
- Université Paris-Saclay, CNRS, INRAe, Université Paris Cité, Université d'Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Gif-sur-Yvette, France
| | - Michael Hodges
- Université Paris-Saclay, CNRS, INRAe, Université Paris Cité, Université d'Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Gif-sur-Yvette, France.
| | - Nathalie Glab
- Université Paris-Saclay, CNRS, INRAe, Université Paris Cité, Université d'Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Gif-sur-Yvette, France.
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Liepman AH, Jaworski M, Ramirez-Lopez C. Spectrophotometric Assays for Measuring Hydroxypyruvate Reductase Activity. Methods Mol Biol 2024; 2792:77-81. [PMID: 38861079 DOI: 10.1007/978-1-0716-3802-6_6] [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] [Indexed: 06/12/2024]
Abstract
Hydroxypyruvate reductase (HPR; EC 1.1.1.81) activity is integral to the photorespiratory pathway. Within photorespiration, HPR catalyzes the reduction of hydroxypyruvate, a product of the serine:glyoxylate aminotransferase reaction to glycerate, a substrate for glycerate kinase, using NADH as cofactor. Here we detail a spectrophotometric assay for measuring HPR activity in vitro by following the consumption of NADH at 340 nm.
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Affiliation(s)
- Aaron H Liepman
- Biology Department, Eastern Michigan University, Ypsilanti, MI, USA.
| | - Mara Jaworski
- Biology Department, Eastern Michigan University, Ypsilanti, MI, USA
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Mauve C, Oury C, Glab N, Hodges M. Measuring Phosphoglycolate Phosphatase Activity Using NMR Detection of Glycolate. Methods Mol Biol 2024; 2792:19-27. [PMID: 38861075 DOI: 10.1007/978-1-0716-3802-6_2] [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] [Indexed: 06/12/2024]
Abstract
Besides the historical and traditional use of nuclear magnetic resonance (NMR) spectroscopy as a structure elucidation tool for proteins and metabolites, its quantification ability allows the determination of metabolite amounts and therefore enzymatic activity measurements. For this purpose, 1H-NMR with adapted water pulse pre-saturation sequences and calibration curves with commercial standard solutions can be used to quantify the photorespiratory cycle intermediates, 2-phosphoglycolate and glycolate, associated with the phosphoglycolate phosphatase reaction. The intensity of the 1H-NMR signal of glycolate produced by the activity of purified recombinant Arabidopsis thaliana PGLP1 can therefore be used to determine PGLP1 enzymatic activities and kinetic parameters.
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Affiliation(s)
- Caroline Mauve
- Université Paris-Saclay, CNRS, INRAe, Université Paris Cité, Université d'Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Gif-sur-Yvette, France.
| | - Céline Oury
- Université Paris-Saclay, CNRS, INRAe, Université Paris Cité, Université d'Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Gif-sur-Yvette, France
| | - Nathalie Glab
- Université Paris-Saclay, CNRS, INRAe, Université Paris Cité, Université d'Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Gif-sur-Yvette, France
| | - Michael Hodges
- Université Paris-Saclay, CNRS, INRAe, Université Paris Cité, Université d'Evry, Institute of Plant Sciences Paris-Saclay (IPS2), Gif-sur-Yvette, France.
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Saini D, Rao DE, Bapatla RB, Aswani V, Raghavendra AS. Measurement of Photorespiratory Cycle Enzyme Activities in Leaves Exposed to Abiotic Stress. Methods Mol Biol 2024; 2832:145-161. [PMID: 38869793 DOI: 10.1007/978-1-0716-3973-3_10] [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] [Indexed: 06/14/2024]
Abstract
Photorespiration, an essential metabolic component, is a classic example of interactions between the intracellular compartments of a plant cell: the chloroplast, peroxisome, mitochondria, and cytoplasm. The photorespiratory pathway is often modulated by abiotic stress and is considered an adaptive response. Monitoring the patterns of key enzymes located in different subcellular components would be an ideal approach to assessing the modulation of the photorespiratory metabolism under abiotic stress. This chapter describes the procedures for assaying several individual enzyme activities of key photorespiratory enzymes and evaluating their response to oxidative/photooxidative stress. It is essential to ascertain the presence of stress in the experimental material. Therefore, procedures for typical abiotic stress induction in leaves by highlighting without or with menadione (an oxidant that targets mitochondria) are also included.
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Affiliation(s)
- Deepak Saini
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Duvvarapu Easwar Rao
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Ramesh Babu Bapatla
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Vetcha Aswani
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Agepati S Raghavendra
- Department of Plant Sciences, School of Life Sciences, University of Hyderabad, Hyderabad, India
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Timm S, Jahnke K, Cosse M, Selinski J. Mitochondrial Dihydrolipoamide Dehydrogenase (mtLPD1): Expression, Purification, Activity, and Redox Regulation. Methods Mol Biol 2024; 2792:51-75. [PMID: 38861078 DOI: 10.1007/978-1-0716-3802-6_5] [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] [Indexed: 06/12/2024]
Abstract
Mitochondrial dihydrolipoamide dehydrogenase (mtLPD1) is a central enzyme in primary carbon metabolism, since its function is required to drive four multienzymes involved in photorespiration, the tricarboxylic acid (TCA) cycle, and the degradation of branched-chain amino acids. However, in illuminated, photosynthesizing tissue a vast amount of mtLPD1 is necessary for glycine decarboxylase (GDC), the key enzyme of photorespiration. In light of the shared role, the functional characterization of mtLPD1 is necessary to understand how the three pathways might interact under different environmental scenarios. This includes the determination of the biochemical properties and all potential regulatory mechanisms, respectively. With regards to the latter, regulation can occur through multiple levels including effector molecules, cofactor availability, or posttranslational modifications (PTM), which in turn decrease or increase the activity of each enzymatic reaction. Gaining a comprehensive overview on all these aspects would ultimately facilitate the interpretation of the metabolic interplay of the pathways within the whole subcellular network or even function as a proof of concept for genetic engineering approaches. Here, we describe the typical workflow how to clone, express, and purify plant mtLPD1 for biochemical characterization and how to analyze potential redox regulatory mechanisms in vitro and in planta.
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Affiliation(s)
- Stefan Timm
- Plant Physiology Department, University of Rostock, Rostock, Germany.
| | - Kathrin Jahnke
- Plant Physiology Department, University of Rostock, Rostock, Germany
| | - Maike Cosse
- Department of Plant Cell Biology, Botanical Institute, Christian-Albrechts University Kiel, Kiel, Germany
| | - Jennifer Selinski
- Department of Plant Cell Biology, Botanical Institute, Christian-Albrechts University Kiel, Kiel, Germany.
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Krämer K, Brock J, Heyer AG. Interaction of Nitrate Assimilation and Photorespiration at Elevated CO 2. FRONTIERS IN PLANT SCIENCE 2022; 13:897924. [PMID: 35845694 PMCID: PMC9284316 DOI: 10.3389/fpls.2022.897924] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Accepted: 06/07/2022] [Indexed: 06/15/2023]
Abstract
It has been shown repeatedly that exposure to elevated atmospheric CO2 causes an increased C/N ratio of plant biomass that could result from either increased carbon or - in relation to C acquisition - reduced nitrogen assimilation. Possible reasons for diminished nitrogen assimilation are controversial, but an impact of reduced photorespiration at elevated CO2 has frequently been implied. Using a mutant defective in peroxisomal hydroxy-pyruvate reductase (hpr1-1) that is hampered in photorespiratory turnover, we show that indeed, photorespiration stimulates the glutamine-synthetase 2 (GS) / glutamine-oxoglutarate-aminotransferase (GOGAT) cycle, which channels ammonia into amino acid synthesis. However, mathematical flux simulations demonstrated that nitrate assimilation was not reduced at elevated CO2, pointing to a dilution of nitrogen containing compounds by assimilated carbon at elevated CO2. The massive growth reduction in the hpr1-1 mutant does not appear to result from nitrogen starvation. Model simulations yield evidence for a loss of cellular energy that is consumed in supporting high flux through the GS/GOGAT cycle that results from inefficient removal of photorespiratory intermediates. This causes a futile cycling of glycolate and hydroxy-pyruvate. In addition to that, accumulation of serine and glycine as well as carboxylates in the mutant creates a metabolic imbalance that could contribute to growth reduction.
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Krämer K, Kepp G, Brock J, Stutz S, Heyer AG. Acclimation to elevated CO 2 affects the C/N balance by reducing de novo N-assimilation. PHYSIOLOGIA PLANTARUM 2022; 174:e13615. [PMID: 35014037 DOI: 10.1111/ppl.13615] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 12/13/2021] [Accepted: 12/15/2021] [Indexed: 06/14/2023]
Abstract
Plants exposed to elevated atmospheric CO2 concentrations show an increased photosynthetic activity. However, after prolonged exposure, the activity declines. This acclimation to elevated CO2 is accompanied by a rise in the carbon-to-nitrogen ratio of the biomass. Hence, increased sugar accumulation and sequential downregulation of photosynthetic genes, as well as nitrogen depletion and reduced protein content, have been hypothesized as the cause of low photosynthetic performance. However, the reason for reduced nitrogen content in plants at high CO2 is unclear. Here, we show that reduced photorespiration at increased CO2 -to-O2 ratio leads to reduced de novo assimilation of nitrate, thus shifting the C/N balance. Metabolic modeling of acclimated and non-acclimated plants revealed the photorespiratory pathway to function as a sink for already assimilated nitrogen during the light period, providing carbon skeletons for de novo assimilation. At high CO2 , low photorespiratory activity resulted in diminished nitrogen assimilation and eventually resulted in reduced carbon assimilation. For the hpr1-1 mutant, defective in reduction of hydroxy-pyruvate, metabolic simulations show that turnover of photorespiratory metabolites is expanded into the night. Comparison of simulations for hpr1-1 with those for the wild type allowed investigating the effect of a perturbed photorespiration on N-assimilation.
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Affiliation(s)
- Konrad Krämer
- Institute of Biomaterials and Biomolecular Systems, Department of Plant Biotechnology, University of Stuttgart, Stuttgart, Germany
| | - Gabi Kepp
- Institute of Biomaterials and Biomolecular Systems, Department of Plant Biotechnology, University of Stuttgart, Stuttgart, Germany
| | - Judith Brock
- Institute of Biomaterials and Biomolecular Systems, Department of Plant Biotechnology, University of Stuttgart, Stuttgart, Germany
| | - Simon Stutz
- Institute of Biomaterials and Biomolecular Systems, Department of Plant Biotechnology, University of Stuttgart, Stuttgart, Germany
| | - Arnd G Heyer
- Institute of Biomaterials and Biomolecular Systems, Department of Plant Biotechnology, University of Stuttgart, Stuttgart, Germany
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Sekula B, Ruszkowski M, Dauter Z. Structural Analysis of Phosphoserine Aminotransferase (Isoform 1) From Arabidopsis thaliana- the Enzyme Involved in the Phosphorylated Pathway of Serine Biosynthesis. FRONTIERS IN PLANT SCIENCE 2018; 9:876. [PMID: 30034403 PMCID: PMC6043687 DOI: 10.3389/fpls.2018.00876] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 06/05/2018] [Indexed: 05/17/2023]
Abstract
Phosphoserine aminotransferase (PSAT) is a pyridoxal 5'-phosphate (PLP)-dependent enzyme that catalyzes the conversion of 3-phosphohydroxypyruvate (3-PHP) to 3-phosphoserine (PSer) in an L-glutamate (Glu)-linked reversible transamination reaction. This process proceeds through a bimolecular ping-pong mechanism and in plants takes place in plastids. It is a part of the phosphorylated pathway of serine biosynthesis, one of three routes recognized in plant organisms that yield serine. In this three-step biotransformation, 3-phosphoglycerate (3-PGA) delivered from plastidial glycolysis and Calvin cycle is oxidized by 3-PGA dehydrogenase. Then, 3-PHP is subjected to transamination with Glu to yield PSer and α-ketoglutarate (AKG). In the last step of the pathway, serine is produced by the action of phosphoserine phosphatase. Here we present the structural characterization of PSAT isoform 1 from Arabidopsis thaliana (AtPSAT1), a dimeric S-shaped protein that truncated of its 71-residue-long chloroplast-targeting signal peptide. Three crystal structures of AtPSAT1 captured at different stages of the reaction: (i) internal aldimine state with PLP covalently bound to the catalytic K265, (ii) holoenzyme in complex with pyridoxamine-5'-phosphate (PMP) after transfer of the amino group from glutamate and (iii) the geminal diamine intermediate state wherein the cofactor is covalently bound to both, K265 and PSer. These snapshots over the course of the reaction present detailed architecture of AtPSAT1 and allow for the comparison of this plant enzyme with other PSATs. Conformational changes of the protein during the catalytic event concern (i) the neighborhood of K265 when the amino group is transferred to the cofactor to form PMP and (ii) movement of the gate-keeping loop (residues 391-401) upon binding of 3-PHP and PSer. The latter conformational change of the loop may likely be one of key elements that regulate catalytic activity of PSATs.
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