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Michimori Y, Yokooji Y, Atomi H. An energy-conserving reaction in amino acid metabolism catalyzed by arginine synthetase. Proc Natl Acad Sci U S A 2024; 121:e2401313121. [PMID: 38602916 PMCID: PMC11032458 DOI: 10.1073/pnas.2401313121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2024] [Accepted: 02/28/2024] [Indexed: 04/13/2024] Open
Abstract
All forms of life are presumed to synthesize arginine from citrulline via a two-step pathway consisting of argininosuccinate synthetase and argininosuccinate lyase using citrulline, adenosine 5'-triphosphate (ATP), and aspartate as substrates. Conversion of arginine to citrulline predominantly proceeds via hydrolysis. Here, from the hyperthermophilic archaeon Thermococcus kodakarensis, we identified an enzyme which we designate "arginine synthetase". In arginine synthesis, the enzyme converts citrulline, ATP, and free ammonia to arginine, adenosine 5'-diphosphate (ADP), and phosphate. In the reverse direction, arginine synthetase conserves the energy of arginine deimination and generates ATP from ADP and phosphate while releasing ammonia. The equilibrium constant of this reaction at pH 7.0 is [Cit][ATP][NH3]/[Arg][ADP][Pi] = 10.1 ± 0.7 at 80 °C, corresponding to a ΔG°' of -6.8 ± 0.2 kJ mol-1. Growth of the gene disruption strain was compared to the host strain in medium composed of amino acids. The results suggested that arginine synthetase is necessary in providing ornithine, the precursor for proline biosynthesis, as well as in generating ATP. Growth in medium supplemented with citrulline indicated that arginine synthetase can function in the direction of arginine synthesis. The enzyme is widespread in nature, including bacteria and eukaryotes, and catalyzes a long-overlooked energy-conserving reaction in microbial amino acid metabolism. Along with ornithine transcarbamoylase and carbamate kinase, the pathway identified here is designated the arginine synthetase pathway.
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Affiliation(s)
- Yuta Michimori
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto615-8510, Japan
- Top Global University Program, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto615-8510, Japan
| | - Yuusuke Yokooji
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto615-8510, Japan
| | - Haruyuki Atomi
- Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto615-8510, Japan
- Top Global University Program, Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Kyoto615-8510, Japan
- Integrated Research Center for Carbon Negative Science, Institute of Advanced Energy, Kyoto University, Uji611-0011, Japan
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Vali SW, Haja DK, Brand RA, Adams MWW, Lindahl PA. The Pyrococcus furiosus ironome is dominated by [Fe 4S 4] 2+ clusters or thioferrate-like iron depending on the availability of elemental sulfur. J Biol Chem 2021; 296:100710. [PMID: 33930466 PMCID: PMC8219758 DOI: 10.1016/j.jbc.2021.100710] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 04/12/2021] [Accepted: 04/22/2021] [Indexed: 11/28/2022] Open
Abstract
Pyrococcus furiosus is a hyperthermophilic anaerobic archaeon whose metabolism depends on whether elemental sulfur is (+S0) or is not (-S0) included in growth medium. Under +S0 conditions, expression of respiratory hydrogenase declines while respiratory membrane-bound sulfane reductase and the putative iron-storage protein IssA increase. Our objective was to investigate the iron content of WT and ΔIssA cells under these growth conditions using Mössbauer spectroscopy. WT-S0 cells contained ∼1 mM Fe, with ∼85% present as two spectroscopically distinct forms of S = 0 [Fe4S4]2+ clusters; the remainder was mainly high-spin FeII. WT+S0 cells contained 5 to 9 mM Fe, with 75 to 90% present as magnetically ordered thioferrate-like (TFL) iron nanoparticles. TFL iron was similar to chemically defined thioferrates; both consisted of FeIII ions coordinated by an S4 environment, and both exhibited strong coupling between particles causing high applied fields to have little spectral effect. At high temperatures with magnetic hyperfine interactions abolished, TFL iron exhibited two doublets overlapping those of [Fe4S4]2+ clusters in -S0 cells. This coincidence arose because of similar coordination environments of TFL iron and cluster iron. The TFL structure was more heterogeneous in the presence of IssA. Presented data suggest that IssA may coordinate insoluble iron sulfides as TFL iron, formed as a byproduct of anaerobic sulfur respiration under high iron conditions, which thereby reduces its toxicity to the cell. This was the first Mössbauer characterization of the ironome of an archaeon, and it illustrates differences relative to the iron content of better-studied bacteria such as Escherichia coli.
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Affiliation(s)
- Shaik Waseem Vali
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA
| | - Dominik K Haja
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Richard A Brand
- Faculty of Physics, University of Duisburg-Essen, Duisburg, Germany; Institute of Nanotechnology, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
| | - Michael W W Adams
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, USA
| | - Paul A Lindahl
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas, USA; Department of Chemistry, Texas A&M University, College Station, Texas, USA.
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Genetic examination and mass balance analysis of pyruvate/amino acid oxidation pathways in the hyperthermophilic archaeon Thermococcus kodakarensis. J Bacteriol 2014; 196:3831-9. [PMID: 25157082 DOI: 10.1128/jb.02021-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The present study investigated the simultaneous oxidation of pyruvate and amino acids during H2-evolving growth of the hyperthermophilic archaeon Thermococcus kodakarensis. The comparison of mass balance between a cytosolic hydrogenase (HYH)-deficient strain (the ΔhyhBGSL strain) and the parent strain indicated that NADPH generated via H2 uptake by HYH was consumed by reductive amination of 2-oxoglutarate catalyzed by glutamate dehydrogenase. Further examinations were done to elucidate functions of three enzymes potentially involved in pyruvate oxidation: pyruvate formate-lyase (PFL), pyruvate:ferredoxin oxidoreductase (POR), and 2-oxoisovalerate:ferredoxin oxidoreductase (VOR) under the HYH-deficient background in T. kodakarensis. No significant change was observed by deletion of pflDA, suggesting that PFL had no critical role in pyruvate oxidation. The growth properties and mass balances of ΔporDAB and ΔvorDAB strains indicated that POR and VOR specifically functioned in oxidation of pyruvate and branched-chain amino acids, respectively, and the lack of POR or VOR was compensated for by promoting the oxidation of another substrate driven by the remaining oxidoreductase. The H2 yields from the consumed pyruvate and amino acids were increased from 31% by the parent strain to 67% and 82% by the deletion of hyhBGSL and double deletion of hyhBGSL and vorDAB, respectively. Significant discrepancies in the mass balances were observed in excess formation of acetate and NH3, suggesting the presence of unknown metabolisms in T. kodakarensis grown in the rich medium containing pyruvate.
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The bifunctional pyruvate decarboxylase/pyruvate ferredoxin oxidoreductase from Thermococcus guaymasensis. ARCHAEA-AN INTERNATIONAL MICROBIOLOGICAL JOURNAL 2014; 2014:349379. [PMID: 24982594 PMCID: PMC4058850 DOI: 10.1155/2014/349379] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/15/2014] [Accepted: 04/29/2014] [Indexed: 11/18/2022]
Abstract
The hyperthermophilic archaeon Thermococcus guaymasensis produces ethanol as a metabolic end product, and an alcohol dehydrogenase (ADH) catalyzing the reduction of acetaldehyde to ethanol has been purified and characterized. However, the enzyme catalyzing the formation of acetaldehyde has not been identified. In this study an enzyme catalyzing the production of acetaldehyde from pyruvate was purified and characterized from T. guaymasensis under strictly anaerobic conditions. The enzyme had both pyruvate decarboxylase (PDC) and pyruvate ferredoxin oxidoreductase (POR) activities. It was oxygen sensitive, and the optimal temperatures were 85°C and >95°C for the PDC and POR activities, respectively. The purified enzyme had activities of 3.8 ± 0.22 U mg(-1) and 20.2 ± 1.8 U mg(-1), with optimal pH-values of 9.5 and 8.4 for each activity, respectively. Coenzyme A was essential for both activities, although it did not serve as a substrate for the former. Enzyme kinetic parameters were determined separately for each activity. The purified enzyme was a heterotetramer. The sequences of the genes encoding the subunits of the bifunctional PDC/POR were determined. It is predicted that all hyperthermophilic β -keto acids ferredoxin oxidoreductases are bifunctional, catalyzing the activities of nonoxidative and oxidative decarboxylation of the corresponding β -keto acids.
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Genetic examination of initial amino acid oxidation and glutamate catabolism in the hyperthermophilic archaeon Thermococcus kodakarensis. J Bacteriol 2013; 195:1940-8. [PMID: 23435976 DOI: 10.1128/jb.01979-12] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Amino acid catabolism in Thermococcales is presumed to proceed via three steps: oxidative deamination of amino acids by glutamate dehydrogenase (GDH) or aminotransferases, oxidative decarboxylation by 2-oxoacid:ferredoxin oxidoreductases (KOR), and hydrolysis of acyl-coenzyme A (CoA) by ADP-forming acyl-CoA synthetases (ACS). Here, we performed a genetic examination of enzymes involved in Glu catabolism in Thermococcus kodakarensis. Examination of amino acid dehydrogenase activities in cell extracts of T. kodakarensis KUW1 (ΔpyrF ΔtrpE) revealed high NADP-dependent GDH activity, along with lower levels of NAD-dependent activity. NADP-dependent activities toward Gln/Ala/Val/Cys and an NAD-dependent threonine dehydrogenase activity were also detected. In KGDH1, a gene disruption strain of T. kodakarensis GDH (Tk-GDH), only threonine dehydrogenase activity was detected, indicating that all other activities were dependent on Tk-GDH. KGDH1 could not grow in a medium in which growth was dependent on amino acid catabolism, implying that Tk-GDH is the only enzyme that can discharge the electrons (to NADP(+)/NAD(+)) released from amino acids in their oxidation to 2-oxoacids. In a medium containing excess pyruvate, KGDH1 displayed normal growth, but higher degrees of amino acid catabolism were observed compared to those for KUW1, suggesting that Tk-GDH functions to suppress amino acid oxidation and plays an anabolic role under this condition. We further constructed disruption strains of 2-oxoglutarate:ferredoxin oxidoreductase and succinyl-CoA synthetase. The two strains displayed growth defects in both media compared to KUW1. Succinate generation was not observed in these strains, indicating that the two enzymes are solely responsible for Glu catabolism among the multiple KOR and ACS enzymes in T. kodakarensis.
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Ozawa Y, Siddiqui MA, Takahashi Y, Urushiyama A, Ohmori D, Yamakura F, Arisaka F, Imai T. Indolepyruvate ferredoxin oxidoreductase: An oxygen-sensitive iron-sulfur enzyme from the hyperthermophilic archaeon Thermococcus profundus. J Biosci Bioeng 2012; 114:23-7. [PMID: 22608551 DOI: 10.1016/j.jbiosc.2012.02.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 02/08/2012] [Accepted: 02/15/2012] [Indexed: 10/28/2022]
Abstract
Thermococcus profundus is a strictly anaerobic sulfur-dependent archaeon that grows optimally at 80°C by peptide fermentation. Indolepyruvate ferredoxin oxidoreductase (IOR), an enzyme involved in the peptide fermentation pathway, was purified to homogeneity from the archaeon under strictly anaerobic conditions. The maximal activity was obtained above the boiling temperature of water (105°C), with a half-life of 62min at 100°C and 20min at 105°C. IOR was oxygen-sensitive with a half-life of 7h at 25°C under aerobic conditions. The specific activity of T. profundus IOR was found to be dependent on the number of [4Fe-4S] clusters in the enzyme.
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Affiliation(s)
- Yukiko Ozawa
- Department of Life Science and Graduate School of Life Science, Rikkyo (St. Paul's) University, Toshima-ku, Tokyo 171-8501, Japan
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Ikeda T, Yamamoto M, Arai H, Ohmori D, Ishii M, Igarashi Y. Enzymatic and electron paramagnetic resonance studies of anabolic pyruvate synthesis by pyruvate: ferredoxin oxidoreductase from Hydrogenobacter thermophilus. FEBS J 2009; 277:501-10. [PMID: 20015072 DOI: 10.1111/j.1742-4658.2009.07506.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Pyruvate: ferredoxin oxidoreductase (POR; EC 1.2.7.1) catalyzes the thiamine pyrophosphate-dependent oxidative decarboxylation of pyruvate to form acetyl-CoA and CO(2). The thermophilic, obligate chemolithoautotrophic hydrogen-oxidizing bacterium, Hydrogenobacter thermophilus TK-6, assimilates CO(2) via the reductive tricarboxylic acid cycle. In this cycle, POR acts as pyruvate synthase catalyzing the reverse reaction (i.e. reductive carboxylation of acetyl-CoA) to form pyruvate. The pyruvate synthesis reaction catalyzed by POR is an energetically unfavorable reaction and requires a strong reductant. Moreover, the reducing equivalents must be supplied via its physiological electron mediator, a small iron-sulfur protein ferredoxin. Therefore, the reaction is difficult to demonstrate in vitro and the reaction mechanism has been poorly understood. In the present study, we coupled the decarboxylation of 2-oxoglutarate catalyzed by 2-oxoglutarate: ferredoxin oxidoreductase (EC 1.2.7.3), which generates sufficiently low-potential electrons to reduce ferredoxin, to drive the energy-demanding pyruvate synthesis by POR. We demonstrate that H. thermophilus POR catalyzes pyruvate synthesis from acetyl-CoA and CO(2), confirming the operation of the reductive tricarboxylic acid cycle in this bacterium. We also measured the electron paramagnetic resonance spectra of the POR intermediates in both the forward and reverse reactions, and demonstrate the intermediacy of a 2-(1-hydroxyethyl)- or 2-(1-hydroxyethylidene)-thiamine pyrophosphate radical in both reactions. The reaction mechanism of the reductive carboxylation of acetyl-CoA is also discussed.
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Affiliation(s)
- Takeshi Ikeda
- Department of Biotechnology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan
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