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Partipilo M, Claassens NJ, Slotboom DJ. A Hitchhiker's Guide to Supplying Enzymatic Reducing Power into Synthetic Cells. ACS Synth Biol 2023; 12:947-962. [PMID: 37052416 PMCID: PMC10127272 DOI: 10.1021/acssynbio.3c00070] [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: 01/31/2023] [Indexed: 04/14/2023]
Abstract
The construction from scratch of synthetic cells by assembling molecular building blocks is unquestionably an ambitious goal from a scientific and technological point of view. To realize functional life-like systems, minimal enzymatic modules are required to sustain the processes underlying the out-of-equilibrium thermodynamic status hallmarking life, including the essential supply of energy in the form of electrons. The nicotinamide cofactors NAD(H) and NADP(H) are the main electron carriers fueling reductive redox reactions of the metabolic network of living cells. One way to ensure the continuous availability of reduced nicotinamide cofactors in a synthetic cell is to build a minimal enzymatic module that can oxidize an external electron donor and reduce NAD(P)+. In the diverse world of metabolism there is a plethora of potential electron donors and enzymes known from living organisms to provide reducing power to NAD(P)+ coenzymes. This perspective proposes guidelines to enable the reduction of nicotinamide cofactors enclosed in phospholipid vesicles, while avoiding high burdens of or cross-talk with other encapsulated metabolic modules. By determining key requirements, such as the feasibility of the reaction and transport of the electron donor into the cell-like compartment, we select a shortlist of potentially suitable electron donors. We review the most convenient proteins for the use of these reducing agents, highlighting their main biochemical and structural features. Noting that specificity toward either NAD(H) or NADP(H) imposes a limitation common to most of the analyzed enzymes, we discuss the need for specific enzymes─transhydrogenases─to overcome this potential bottleneck.
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Affiliation(s)
- Michele Partipilo
- Department
of Biochemistry, Groningen Institute of Biomolecular Sciences &
Biotechnology, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
| | - Nico J. Claassens
- Laboratory
of Microbiology, Wageningen University, Stippeneng 4, 6708 WE Wageningen, The Netherlands
| | - Dirk Jan Slotboom
- Department
of Biochemistry, Groningen Institute of Biomolecular Sciences &
Biotechnology, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands
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2
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Lund M, Heaton R, Hargreaves IP, Gregersen N, Olsen RKJ. Odd- and even-numbered medium-chained fatty acids protect against glutathione depletion in very long-chain acyl-CoA dehydrogenase deficiency. Biochim Biophys Acta Mol Cell Biol Lipids 2023; 1868:159248. [PMID: 36356723 DOI: 10.1016/j.bbalip.2022.159248] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 10/09/2022] [Accepted: 10/17/2022] [Indexed: 11/09/2022]
Abstract
Recent trials have reported the ability of triheptanoin to improve clinical outcomes for the severe symptoms associated with long-chain fatty acid oxidation disorders, including very long-chain acyl-CoA dehydrogenase (VLCAD) deficiency. However, the milder myopathic symptoms are still challenging to treat satisfactorily. Myopathic pathogenesis is multifactorial, but oxidative stress is an important component. We have previously shown that metabolic stress increases the oxidative burden in VLCAD-deficient cell lines and can deplete the antioxidant glutathione (GSH). We investigated whether medium-chain fatty acids provide protection against GSH depletion during metabolic stress in VLCAD-deficient fibroblasts. To investigate the effect of differences in anaplerotic capacity, we included both even-(octanoate) and odd-numbered (heptanoate) medium-chain fatty acids. Overall, we show that modulation of the concentration of medium-chain fatty acids in culture media affects levels of GSH retained during metabolic stress in VLCAD-deficient cell lines but not in controls. Lowered glutamine concentration in the culture media during metabolic stress led to GSH depletion and decreased viability in VLCAD deficient cells, which could be rescued by both heptanoate and octanoate in a dose-dependent manner. Unlike GSH levels, the levels of total thiols increased after metabolic stress exposure, the size of this increase was not affected by differences in cell culture medium concentrations of glutamine, heptanoate or octanoate. Addition of a PPAR agonist further exacerbated stress-related GSH-depletion and viability loss, requiring higher concentrations of fatty acids to restore GSH levels and cell viability. Both odd- and even-numbered medium-chain fatty acids efficiently protect VLCADdeficient cells against metabolic stress-induced antioxidant depletion.
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Affiliation(s)
- Martin Lund
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, Palle Juel-Jensens Boulevard 99, 8200 Aarhus, Denmark.
| | - Robert Heaton
- School of Pharmacy, Liverpool John Moore University, Byrom Street, Liverpool L3 3AF, United Kingdom
| | - Iain P Hargreaves
- School of Pharmacy, Liverpool John Moore University, Byrom Street, Liverpool L3 3AF, United Kingdom
| | - Niels Gregersen
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, Palle Juel-Jensens Boulevard 99, 8200 Aarhus, Denmark
| | - Rikke K J Olsen
- Research Unit for Molecular Medicine, Department of Clinical Medicine, Aarhus University and Aarhus University Hospital, Palle Juel-Jensens Boulevard 99, 8200 Aarhus, Denmark.
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3
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Francisco A, Figueira TR, Castilho RF. Mitochondrial NAD(P) + Transhydrogenase: From Molecular Features to Physiology and Disease. Antioxid Redox Signal 2022; 36:864-884. [PMID: 34155914 DOI: 10.1089/ars.2021.0111] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Significance: Proton-translocating NAD(P)+ transhydrogenase, also known as nicotinamide nucleotide transhydrogenase (NNT), catalyzes a reversible reaction coupling the protonmotive force across the inner mitochondrial membrane and hydride (H-, a proton plus two electrons) transfer between the mitochondrial pools of NAD(H) and NADP(H). The forward NNT reaction is a source of NADPH in the mitochondrial matrix, fueling antioxidant and biosynthetic pathways with reductive potential. Despite the greater emphasis given to the net forward reaction, the reverse NNT reaction that oxidizes NADPH also occurs in physiological and pathological conditions. Recent Advances: NNT (dys)function has been linked to various metabolic pathways and disease phenotypes. Most of these findings have been based on spontaneous loss-of-function Nnt mutations found in the C57BL/6J mouse strain (NntC57BL/6J mutation) and disease-causing Nnt mutations in humans. The present review focuses on recent advances based on the mouse NntC57BL/6J mutation. Critical Issues: Most studies associating NNT function with disease phenotypes have been based on comparisons between different strains of inbred mice (with or without the NntC57BL/6J mutation), which creates uncertainties over the actual contribution of NNT in the context of other potential genetic modifiers. Future Directions: Future research might contribute to understanding the role of NNT in pathological conditions and elucidate how NNT regulates physiological signaling through its forward and reverse reactions. The importance of NNT in redox balance and tumor cell proliferation makes it a potential target of new therapeutic strategies for oxidative-stress-mediated diseases and cancer. Antioxid. Redox Signal. 36, 864-884.
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Affiliation(s)
- Annelise Francisco
- Department of Pathology, Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas, Brazil
| | - Tiago Rezende Figueira
- School of Physical Education and Sport of Ribeirão Preto, University of São Paulo (USP), Ribeirão Preto, Brazil
| | - Roger Frigério Castilho
- Department of Pathology, Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas, Brazil
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4
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Theodosiou E, Tüllinghoff A, Toepel J, Bühler B. Exploitation of Hetero- and Phototrophic Metabolic Modules for Redox-Intensive Whole-Cell Biocatalysis. Front Bioeng Biotechnol 2022; 10:855715. [PMID: 35497353 PMCID: PMC9043136 DOI: 10.3389/fbioe.2022.855715] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Accepted: 03/09/2022] [Indexed: 11/13/2022] Open
Abstract
The successful realization of a sustainable manufacturing bioprocess and the maximization of its production potential and capacity are the main concerns of a bioprocess engineer. A main step towards this endeavor is the development of an efficient biocatalyst. Isolated enzyme(s), microbial cells, or (immobilized) formulations thereof can serve as biocatalysts. Living cells feature, beside active enzymes, metabolic modules that can be exploited to support energy-dependent and multi-step enzyme-catalyzed reactions. Metabolism can sustainably supply necessary cofactors or cosubstrates at the expense of readily available and cheap resources, rendering external addition of costly cosubstrates unnecessary. However, for the development of an efficient whole-cell biocatalyst, in depth comprehension of metabolic modules and their interconnection with cell growth, maintenance, and product formation is indispensable. In order to maximize the flux through biosynthetic reactions and pathways to an industrially relevant product and respective key performance indices (i.e., titer, yield, and productivity), existing metabolic modules can be redesigned and/or novel artificial ones established. This review focuses on whole-cell bioconversions that are coupled to heterotrophic or phototrophic metabolism and discusses metabolic engineering efforts aiming at 1) increasing regeneration and supply of redox equivalents, such as NAD(P/H), 2) blocking competing fluxes, and 3) increasing the availability of metabolites serving as (co)substrates of desired biosynthetic routes.
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Affiliation(s)
- Eleni Theodosiou
- Institute of Applied Biosciences, Centre for Research and Technology Hellas, Thessaloniki, Greece
| | - Adrian Tüllinghoff
- Department of Solar Materials, Helmholtz Centre for Environmental Research GmbH—UFZ, Leipzig, Germany
| | - Jörg Toepel
- Department of Solar Materials, Helmholtz Centre for Environmental Research GmbH—UFZ, Leipzig, Germany
| | - Bruno Bühler
- Department of Solar Materials, Helmholtz Centre for Environmental Research GmbH—UFZ, Leipzig, Germany
- *Correspondence: Bruno Bühler,
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5
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Bharath LP, Regan T, Conway R. Regulation of Immune Cell Function by Nicotinamide Nucleotide Transhydrogenase. Am J Physiol Cell Physiol 2022; 322:C666-C673. [PMID: 35138175 PMCID: PMC8977145 DOI: 10.1152/ajpcell.00607.2020] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Redox homeostasis is elemental for the normal physiology of all cell types. Cells use multiple mechanisms to regulate the redox balance tightly. The onset and progression of many metabolic and aging-associated diseases occur due to the dysregulation of redox homeostasis. Thus, it is critical to identify and therapeutically target mechanisms that precipitate abnormalities in redox balance. Reactive oxygen species (ROS) produced within the immune cells regulate homeostasis, hyperimmune and hypoimmune cell responsiveness, apoptosis, immune response to pathogens, and tumor immunity. Immune cells have both cytosolic and organelle-specific redox regulatory systems to maintain appropriate levels of ROS. Nicotinamide nucleotide transhydrogenase (NNT) is an essential mitochondrial redox regulatory protein. Dysregulation of NNT function prevents immune cells from mounting an adequate immune response to pathogens, promotes a chronic inflammatory state associated with aging and metabolic diseases, and initiates conditions related to a dysregulated immune system such as autoimmunity. While many studies have reported on NNT in different cell types, including cancer cells, relatively few studies have explored NNT in immune cells. This review provides an overview of NNT and focuses on the current knowledge of NNT in the immune cells.
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Affiliation(s)
- Leena P Bharath
- Department of Nutrition and Public Health, Merrimack College, North Andover, Massachusetts, United States
| | - Thomas Regan
- Department of Nutrition and Public Health, Merrimack College, North Andover, Massachusetts, United States
| | - Rachel Conway
- Department of Nutrition and Public Health, Merrimack College, North Andover, Massachusetts, United States
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6
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Zöller J, Hong S, Eisinger ML, Anderson M, Radloff M, Desch K, Gennis R, Langer JD. Ligand binding and conformational dynamics of the E. coli nicotinamide nucleotide transhydrogenase revealed by hydrogen/deuterium exchange mass spectrometry. Comput Struct Biotechnol J 2022; 20:5430-5439. [PMID: 36212541 PMCID: PMC9529548 DOI: 10.1016/j.csbj.2022.09.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2022] [Revised: 09/22/2022] [Accepted: 09/22/2022] [Indexed: 11/17/2022] Open
Abstract
Nicotinamide nucleotide transhydrogenases are integral membrane proteins that utilizes the proton motive force to reduce NADP+ to NADPH while converting NADH to NAD+. Atomic structures of various transhydrogenases in different ligand-bound states have become available, and it is clear that the molecular mechanism involves major conformational changes. Here we utilized hydrogen/deuterium exchange mass spectrometry (HDX-MS) to map ligand binding sites and analyzed the structural dynamics of E. coli transhydrogenase. We found different allosteric effects on the protein depending on the bound ligand (NAD+, NADH, NADP+, NADPH). The binding of either NADP+ or NADPH to domain III had pronounced effects on the transmembrane helices comprising the proton-conducting channel in domain II. We also made use of cyclic ion mobility separation mass spectrometry (cyclic IMS-MS) to maximize coverage and sensitivity in the transmembrane domain, showing for the first time that this technique can be used for HDX-MS studies. Using cyclic IMS-MS, we increased sequence coverage from 68 % to 73 % in the transmembrane segments. Taken together, our results provide important new insights into the transhydrogenase reaction cycle and demonstrate the benefit of this new technique for HDX-MS to study ligand binding and conformational dynamics in membrane proteins.
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7
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Energy transfer between the nicotinamide nucleotide transhydrogenase and ATP synthase of Escherichia coli. Sci Rep 2021; 11:21234. [PMID: 34707181 PMCID: PMC8551311 DOI: 10.1038/s41598-021-00651-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 10/15/2021] [Indexed: 11/09/2022] Open
Abstract
Membrane bound nicotinamide nucleotide transhydrogenase (TH) catalyses the hydride transfer from NADH to NADP+. Under physiological conditions, this reaction is endergonic and must be energized by the pmf, coupled to transmembrane proton transport. Recent structures of transhydrogenase holoenzymes suggest new mechanistic details, how the long-distance coupling between hydride transfer in the peripheral nucleotide binding sites and the membrane-localized proton transfer occurs that now must be tested experimentally. Here, we provide protocols for the efficient expression and purification of the Escherichia coli transhydrogenase and its reconstitution into liposomes, alone or together with the Escherichia coli F1F0 ATP synthase. We show that E. coli transhydrogenase is a reversible enzyme that can also work as a NADPH-driven proton pump. In liposomes containing both enzymes, NADPH driven H+-transport by TH is sufficient to instantly fuel ATP synthesis, which adds TH to the pool of pmf generating enzymes. If the same liposomes are energized with ATP, NADPH production by TH is stimulated > sixfold both by a pH gradient or a membrane potential. The presented protocols and results reinforce the tight coupling between hydride transfer in the peripheral nucleotide binding sites and transmembrane proton transport and provide powerful tools to investigate their coupling mechanism.
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Ni Z, Wu J, Li Z, Yuan L, Wang Y, Chen X, Yao J. Enhanced bioproduction of fucosylated oligosaccharide 3-fucosyllactose in engineered Escherichia coli with an improved de novo pathway. Biosci Biotechnol Biochem 2021; 85:1772-1781. [PMID: 33904902 DOI: 10.1093/bbb/zbab074] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Accepted: 04/22/2021] [Indexed: 01/17/2023]
Abstract
3-fucosyllactose (3-FL) and 2'-fucosyllactose (2'-FL), are two important fucosylated oligosaccharides in human milk. Extensive studies on 2'-FL enabled its official approval for use in infant formula. However, development of 3-FL has been somewhat sluggish due to its low content in human milk and poor yield in enlarged production. Here, an α-1,3-fucosyltransferase mutant was introduced into an engineered Escherichia coli (E. coli) capable of producing GDP-L-fucose, leading to a promising 3-FL titer in a 5.0-L bioreactor. To increase the availability of cofactors (NADPH and GTP) for optimized 3-FL production, zwf, pntAB, and gsk genes were successively overexpressed, finally resulting in a higher 3-FL level with a titer of 35.72 g/L and a yield of 0.82 mol 3-FL/mol lactose. Unexpectedly, the deletion of pfkA gene led to a much lower performance of 3-FL production than the control strain. Still, our strategy achieved the highest 3-FL level in E. coli to date.
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Affiliation(s)
- Zhijian Ni
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, P. R. China.,Science Island Branch of Graduate School , University of Science & Technology of China, Hefei, P. R. China
| | - Jinyong Wu
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, P. R. China.,Huainan New Energy Research Center, Institute of Plasma Physics, Chinese Academy of Sciences, Huainan, P. R. China.,Wuhan Zhongke Optics Valley Green Biotechnology Co. Ltd., Wuhan, China
| | - Zhongkui Li
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, P. R. China.,Science Island Branch of Graduate School , University of Science & Technology of China, Hefei, P. R. China
| | - Lixia Yuan
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, P. R. China
| | - Yu Wang
- Wuhan Zhongke Optics Valley Green Biotechnology Co. Ltd., Wuhan, China
| | - Xiangsong Chen
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, P. R. China.,Huainan New Energy Research Center, Institute of Plasma Physics, Chinese Academy of Sciences, Huainan, P. R. China
| | - Jianming Yao
- Institute of Plasma Physics, Hefei Institutes of Physical Science, Chinese Academy of Sciences, Hefei, P. R. China.,Science Island Branch of Graduate School , University of Science & Technology of China, Hefei, P. R. China
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9
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Lack of mitochondrial NADP(H)-transhydrogenase expression in macrophages exacerbates atherosclerosis in hypercholesterolemic mice. Biochem J 2020; 476:3769-3789. [PMID: 31803904 DOI: 10.1042/bcj20190543] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2019] [Revised: 12/04/2019] [Accepted: 12/04/2019] [Indexed: 02/02/2023]
Abstract
The atherosclerosis prone LDL receptor knockout mice (Ldlr-/-, C57BL/6J background) carry a deletion of the NADP(H)-transhydrogenase gene (Nnt) encoding the mitochondrial enzyme that catalyzes NADPH synthesis. Here we hypothesize that both increased NADPH consumption (due to increased steroidogenesis) and decreased NADPH generation (due to Nnt deficiency) in Ldlr-/- mice contribute to establish a macrophage oxidative stress and increase atherosclerosis development. Thus, we compared peritoneal macrophages and liver mitochondria from three C57BL/6J mice lines: Ldlr and Nnt double mutant, single Nnt mutant and wild-type. We found increased oxidants production in both mitochondria and macrophages according to a gradient: double mutant > single mutant > wild-type. We also observed a parallel up-regulation of mitochondrial biogenesis (PGC1a, TFAM and respiratory complexes levels) and inflammatory (iNOS, IL6 and IL1b) markers in single and double mutant macrophages. When exposed to modified LDL, the single and double mutant cells exhibited significant increases in lipid accumulation leading to foam cell formation, the hallmark of atherosclerosis. Nnt deficiency cells showed up-regulation of CD36 and down-regulation of ABCA1 transporters what may explain lipid accumulation in macrophages. Finally, Nnt wild-type bone marrow transplantation into LDLr-/- mice resulted in reduced diet-induced atherosclerosis. Therefore, Nnt plays a critical role in the maintenance of macrophage redox, inflammatory and cholesterol homeostasis, which is relevant for delaying the atherogenesis process.
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Liu S, Skory C, Liang X, Mills D, Qureshi N. Increased ethanol tolerance associated with the pntAB locus of Oenococcus oeni and Lactobacillus buchneri. J Ind Microbiol Biotechnol 2019; 46:1547-1556. [PMID: 31289974 DOI: 10.1007/s10295-019-02209-y] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2019] [Accepted: 06/21/2019] [Indexed: 10/26/2022]
Abstract
Lactobacillus buchneri and Oenococcus oeni are two unique ethanol-tolerant Gram-positive bacteria species. Genome comparison analyses revealed that L. buchneri and O. oeni possess a pntAB locus that was absent in almost all other lactic acid bacteria (LAB) genomes. Our hypothesis is that the pntAB locus contributes to the ethanol tolerance trait of these two distinct ethanol-tolerant organisms. The pntAB locus, consisting of the pntA and pntB genes, codes for NADP(H) transhydrogenase subunits. This membrane-bound transhydrogenase catalyzes the reduction of NADP+ and is known as an important enzyme in maintaining cellular redox balance. In this study, the transhydrogenase operon from L. buchneri NRRL B-30929 and O. oeni PSU-1 were cloned and analyzed. The LbpntB shared 71.0% identity with the O. oeni (OopntB). The entire pntAB locus was expressed in Lactococcus lactis ssp. lactis IL1403 resulting in an increased tolerance to ethanol (6%), butanol (1.8%) and isopropanol (1.8%) when compared to the control strain. However, the recombinant E. coli cells carrying the entire pntAB locus did not show any improved ethanol tolerance. Independent expression of OopntB and LbpntB in recombinant E. coli BL21(DE3)pLysS host demonstrated higher tolerance to ethanol when compared with a control E. coli BL21(DE3)pLysS strain carrying pET28b vector. Ethanol tolerance comparison of E. coli strains carrying LbpntB and OopntB showed that LbpntB conferred higher ethanol tolerance (4.5%) and resulted in greater biomass, while the OopntB conferred lower ethanol tolerance (4.0%) resulted lower biomass. Therefore, the pntB gene from L. buchneri is a better choice in generating higher ethanol tolerance. This is the first study to uncover the role of pntAB locus on ethanol tolerance.
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Li S, Zhuang Z, Wu T, Lin JC, Liu ZX, Zhou LF, Dai T, Lu L, Ju HQ. Nicotinamide nucleotide transhydrogenase-mediated redox homeostasis promotes tumor growth and metastasis in gastric cancer. Redox Biol 2018; 18:246-255. [PMID: 30059901 PMCID: PMC6079569 DOI: 10.1016/j.redox.2018.07.017] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2018] [Revised: 07/20/2018] [Accepted: 07/20/2018] [Indexed: 12/20/2022] Open
Abstract
Overcoming oxidative stress is a critical step for tumor growth and metastasis, however the underlying mechanisms in gastric cancer remain unclear. In this study, we found that overexpression of nicotinamide nucleotide transhydrogenase (NNT) was associated with shorter overall and disease free survival in gastric cancer. The NNT is considered a key antioxidative enzyme based on its ability to regenerate NADPH from NADH. Knockdown of NNT caused significantly NADPH reduction, induced high levels of ROS and significant cell apoptosis under oxidative stress conditions such as glucose deprival and anoikis. In vivo experiments showed that NNT promoted tumor growth, lung metastasis and peritoneal dissemination of gastric cancer. Moreover, intratumoral injection of NNT siRNA significantly suppressed gastric tumor growth in patient-derived xenograft (PDX) models. Overall, our study highlights the crucial functional roles of NNT in redox regulation and tumor progression and thus raises an important therapeutic hypothesis in gastric cancer.
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Affiliation(s)
- Shuai Li
- Department of Biochemistry and Molecular Biology, GMU-GIBH Joint School of Life Sciences, Guangzhou Medical University, Guangzhou 510182, PR China
| | - Zhuonan Zhuang
- Department of Gastrointestinal Surgery, Beijing Tsinghua Changgung Hospital Medical Center, Tsinghua University, Beijing 102218, China
| | - Teng Wu
- Department of Biochemistry and Molecular Biology, GMU-GIBH Joint School of Life Sciences, Guangzhou Medical University, Guangzhou 510182, PR China
| | - Jie-Chun Lin
- Department of Biochemistry and Molecular Biology, GMU-GIBH Joint School of Life Sciences, Guangzhou Medical University, Guangzhou 510182, PR China
| | - Ze-Xian Liu
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, China
| | - Li-Fen Zhou
- Department of Biochemistry and Molecular Biology, GMU-GIBH Joint School of Life Sciences, Guangzhou Medical University, Guangzhou 510182, PR China
| | - Ting Dai
- Department of Biochemistry and Molecular Biology, GMU-GIBH Joint School of Life Sciences, Guangzhou Medical University, Guangzhou 510182, PR China
| | - Lei Lu
- Department of Biochemistry and Molecular Biology, GMU-GIBH Joint School of Life Sciences, Guangzhou Medical University, Guangzhou 510182, PR China
| | - Huai-Qiang Ju
- Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, China.
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12
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Müller V, Chowdhury NP, Basen M. Electron Bifurcation: A Long-Hidden Energy-Coupling Mechanism. Annu Rev Microbiol 2018; 72:331-353. [PMID: 29924687 DOI: 10.1146/annurev-micro-090816-093440] [Citation(s) in RCA: 81] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
A decade ago, a novel mechanism to drive thermodynamically unfavorable redox reactions was discovered that is used in prokaryotes to drive endergonic electron transfer reactions by a direct coupling to an exergonic redox reaction in one soluble enzyme complex. This process is referred to as flavin-based electron bifurcation, or FBEB. An important function of FBEB is that it allows the generation of reduced low-potential ferredoxin (Fdred) from comparably high-potential electron donors such as NADH or molecular hydrogen (H2). Fdred is then the electron donor for anaerobic respiratory chains leading to the synthesis of ATP. In many metabolic scenarios, Fd is reduced by metabolic oxidoreductases and Fdred then drives endergonic metabolic reactions such as H2 production by the reverse, electron confurcation. FBEB is energetically more economical than ATP hydrolysis or reverse electron transport as a driving force for endergonic redox reactions; thus, it does "save" cellular ATP. It is essential for autotrophic growth at the origin of life and also allows for heterotrophic growth on certain low-energy substrates.
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Affiliation(s)
- Volker Müller
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, 60438 Frankfurt, Germany;
| | - Nilanjan Pal Chowdhury
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, 60438 Frankfurt, Germany;
| | - Mirko Basen
- Department of Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University Frankfurt/Main, 60438 Frankfurt, Germany;
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Zhang Q, Padayatti PS, Leung JH. Proton-Translocating Nicotinamide Nucleotide Transhydrogenase: A Structural Perspective. Front Physiol 2017; 8:1089. [PMID: 29312000 PMCID: PMC5742237 DOI: 10.3389/fphys.2017.01089] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 12/11/2017] [Indexed: 01/07/2023] Open
Abstract
Nicotinamide nucleotide transhydrogenase (TH) is an enzyme complex in animal mitochondria and bacteria that utilizes the electrochemical proton gradient across membranes to drive the production of NADPH. The enzyme plays an important role in maintaining the redox balance of cells with implications in aging and a number of human diseases. TH exists as a homodimer with each protomer containing a proton-translocating transmembrane domain and two soluble nucleotide binding domains that mediate hydride transfer between NAD(H) and NADP(H). The three-domain architecture of TH is conserved across species but polypeptide composition differs substantially. The complex domain coupling mechanism of TH is not fully understood despite extensive biochemical and structural characterizations. Herein the progress is reviewed, focusing mainly on structural findings from 3D crystallization of isolated soluble domains and more recently of the transmembrane domain and the holo-enzyme from Thermus thermophilus. A structural perspective and impeding challenges in further elucidating the mechanism of TH are discussed.
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Affiliation(s)
- Qinghai Zhang
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, United States
| | - Pius S Padayatti
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, United States
| | - Josephine H Leung
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA, United States
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Sellés Vidal L, Kelly CL, Mordaka PM, Heap JT. Review of NAD(P)H-dependent oxidoreductases: Properties, engineering and application. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2017; 1866:327-347. [PMID: 29129662 DOI: 10.1016/j.bbapap.2017.11.005] [Citation(s) in RCA: 164] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Revised: 10/27/2017] [Accepted: 11/08/2017] [Indexed: 11/27/2022]
Abstract
NAD(P)H-dependent oxidoreductases catalyze the reduction or oxidation of a substrate coupled to the oxidation or reduction, respectively, of a nicotinamide adenine dinucleotide cofactor NAD(P)H or NAD(P)+. NAD(P)H-dependent oxidoreductases catalyze a large variety of reactions and play a pivotal role in many central metabolic pathways. Due to the high activity, regiospecificity and stereospecificity with which they catalyze redox reactions, they have been used as key components in a wide range of applications, including substrate utilization, the synthesis of chemicals, biodegradation and detoxification. There is great interest in tailoring NAD(P)H-dependent oxidoreductases to make them more suitable for particular applications. Here, we review the main properties and classes of NAD(P)H-dependent oxidoreductases, the types of reactions they catalyze, some of the main protein engineering techniques used to modify their properties and some interesting examples of their modification and application.
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Affiliation(s)
- Lara Sellés Vidal
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Ciarán L Kelly
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - Paweł M Mordaka
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom
| | - John T Heap
- Centre for Synthetic Biology and Innovation, Department of Life Sciences, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom.
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Ho HY, Lin YT, Lin G, Wu PR, Cheng ML. Nicotinamide nucleotide transhydrogenase (NNT) deficiency dysregulates mitochondrial retrograde signaling and impedes proliferation. Redox Biol 2017; 12:916-928. [PMID: 28478381 PMCID: PMC5426036 DOI: 10.1016/j.redox.2017.04.035] [Citation(s) in RCA: 49] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2017] [Accepted: 04/28/2017] [Indexed: 12/25/2022] Open
Abstract
To study the physiological roles of NADH and NADPH homeostasis in cancer, we studied the effect of NNT knockdown on physiology of SK-Hep1 cells. NNT knockdown cells show limited abilities to maintain NAD+ and NADPH levels and have reduced proliferation and tumorigenicity. There is an increased dependence of energy production on oxidative phosphorylation. Studies with stable isotope tracers have revealed that under the new steady-state metabolic condition, the fluxes of TCA and glycolysis decrease while that of reductive carboxylation increases. Increased [α-ketoglutarate]/[succinate] ratio in NNT-deficient cells results in decrease in HIF-1α level and expression of HIF-1α regulated genes. Reduction in NADPH level leads to repression of HDAC1 activity and an increase in p53 acetylation. These findings suggest that NNT is essential to homeostasis of NADH and NADPH pools, anomalies of which affect HIF-1α- and HDAC1-dependent pathways, and hence retrograde response of mitochondria.
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Affiliation(s)
- Hung-Yao Ho
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan; Healthy Aging Research Center, Chang Gung University, Taoyuan 33302, Taiwan; Metabolomics Core Laboratory, Chang Gung University, Taoyuan 33302, Taiwan; Clinical Phenome Center, Chang Gung Memorial Hospital, Linkou, Taoyuan 33302, Taiwan; Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan.
| | - Yu-Ting Lin
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Gigin Lin
- Clinical Phenome Center, Chang Gung Memorial Hospital, Linkou, Taoyuan 33302, Taiwan; Department of Medical Imaging and Intervention, Imaging Core Laboratory, Institute for Radiological Research, Chang Gung Memorial Hospital at Linkou and Chang Gung University, 33302, Taoyuan, Taiwan
| | - Pei-Ru Wu
- Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan
| | - Mei-Ling Cheng
- Graduate Institute of Biomedical Sciences, College of Medicine, Chang Gung University, Taoyuan 33302, Taiwan; Healthy Aging Research Center, Chang Gung University, Taoyuan 33302, Taiwan; Metabolomics Core Laboratory, Chang Gung University, Taoyuan 33302, Taiwan; Clinical Phenome Center, Chang Gung Memorial Hospital, Linkou, Taoyuan 33302, Taiwan
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Metherell LA, Guerra-Assunção JA, Sternberg MJ, David A. Three-Dimensional Model of Human Nicotinamide Nucleotide Transhydrogenase (NNT) and Sequence-Structure Analysis of its Disease-Causing Variations. Hum Mutat 2016; 37:1074-84. [PMID: 27459240 PMCID: PMC5026163 DOI: 10.1002/humu.23046] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2016] [Revised: 06/23/2016] [Accepted: 06/28/2016] [Indexed: 12/22/2022]
Abstract
Defective mitochondrial proteins are emerging as major contributors to human disease. Nicotinamide nucleotide transhydrogenase (NNT), a widely expressed mitochondrial protein, has a crucial role in the defence against oxidative stress. NNT variations have recently been reported in patients with familial glucocorticoid deficiency (FGD) and in patients with heart failure. Moreover, knockout animal models suggest that NNT has a major role in diabetes mellitus and obesity. In this study, we used experimental structures of bacterial transhydrogenases to generate a structural model of human NNT (H‐NNT). Structure‐based analysis allowed the identification of H‐NNT residues forming the NAD binding site, the proton canal and the large interaction site on the H‐NNT dimer. In addition, we were able to identify key motifs that allow conformational changes adopted by domain III in relation to its functional status, such as the flexible linker between domains II and III and the salt bridge formed by H‐NNT Arg882 and Asp830. Moreover, integration of sequence and structure data allowed us to study the structural and functional effect of deleterious amino acid substitutions causing FGD and left ventricular non‐compaction cardiomyopathy. In conclusion, interpretation of the function–structure relationship of H‐NNT contributes to our understanding of mitochondrial disorders.
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Affiliation(s)
- Louise A Metherell
- Centre for Endocrinology, William Harvey Research Institute, Queen Mary University of London, Charterhouse Square, London, UK
| | - José Afonso Guerra-Assunção
- Centre for Molecular Oncology, Barts Cancer Institute, Queen Mary University of London, Charterhouse Square, London, UK
| | - Michael J Sternberg
- Centre for Integrative System Biology and Bioinformatics, Imperial College London, London, UK
| | - Alessia David
- Centre for Integrative System Biology and Bioinformatics, Imperial College London, London, UK.
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Collins J, Zhang T, Huston S, Sun F, Zhang YHP, Fu J. A Hidden Transhydrogen Activity of a FMN-Bound Diaphorase under Anaerobic Conditions. PLoS One 2016; 11:e0154865. [PMID: 27145082 PMCID: PMC4856307 DOI: 10.1371/journal.pone.0154865] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 04/20/2016] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND Redox cofactors of NADH/NADPH participate in many cellular metabolic pathways for facilitating the electron transfer from one molecule to another in redox reactions. Transhydrogenase plays an important role in linking catabolism and anabolism, regulating the ratio of NADH/NADPH in cells. The cytoplasmic transhydrogenases could be useful to engineer synthetic biochemical pathways for the production of high-value chemicals and biofuels. METHODOLOGY/PRINCIPAL FINDINGS A transhydrogenase activity was discovered for a FMN-bound diaphorase (DI) from Geobacillus stearothermophilus under anaerobic conditions. The DI-catalyzed hydride exchange were monitored and characterized between a NAD(P)H and a thio-modified NAD+ analogue. This new function of DI was demonstrated to transfer a hydride from NADPH to NAD+ that was consumed by NAD-specific lactate dehydrogenase and malic dehydrogenase. CONCLUSIONS/SIGNIFICANCE We discover a novel transhydrogenase activity of a FMN-DI by stabilizing the reduced state of FMNH2 under anaerobic conditions. FMN-DI was demonstrated to catalyze the hydride transfer between NADPH and NAD+. In the future, it may be possible to incorporate this FMN-DI into synthetic enzymatic pathways for balancing NADH generation and NADPH consumption for anaerobic production of biofuels and biochemicals.
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Affiliation(s)
- John Collins
- Department of Chemistry, Rutgers University-Camden, Camden, New Jersey 08102, United States of America
| | - Ting Zhang
- Department of Chemistry, Rutgers University-Camden, Camden, New Jersey 08102, United States of America
| | - Scott Huston
- Department of Chemistry, Rutgers University-Camden, Camden, New Jersey 08102, United States of America
| | - Fangfang Sun
- Cell Free Bioinnovations Inc., Blacksburg, Virginia 24060, United States of America
| | - Y.-H. Percival Zhang
- Cell Free Bioinnovations Inc., Blacksburg, Virginia 24060, United States of America
- Department of Biological Systems Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States of America
| | - Jinglin Fu
- Department of Chemistry, Rutgers University-Camden, Camden, New Jersey 08102, United States of America
- Center for Computational and Integrative Biology, Rutgers University-Camden, Camden, New Jersey 08102, United States of America
- * E-mail:
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18
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Dysregulated metabolism contributes to oncogenesis. Semin Cancer Biol 2015; 35 Suppl:S129-S150. [PMID: 26454069 DOI: 10.1016/j.semcancer.2015.10.002] [Citation(s) in RCA: 202] [Impact Index Per Article: 22.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2014] [Revised: 09/30/2015] [Accepted: 10/05/2015] [Indexed: 12/13/2022]
Abstract
Cancer is a disease characterized by unrestrained cellular proliferation. In order to sustain growth, cancer cells undergo a complex metabolic rearrangement characterized by changes in metabolic pathways involved in energy production and biosynthetic processes. The relevance of the metabolic transformation of cancer cells has been recently included in the updated version of the review "Hallmarks of Cancer", where dysregulation of cellular metabolism was included as an emerging hallmark. While several lines of evidence suggest that metabolic rewiring is orchestrated by the concerted action of oncogenes and tumor suppressor genes, in some circumstances altered metabolism can play a primary role in oncogenesis. Recently, mutations of cytosolic and mitochondrial enzymes involved in key metabolic pathways have been associated with hereditary and sporadic forms of cancer. Together, these results demonstrate that aberrant metabolism, once seen just as an epiphenomenon of oncogenic reprogramming, plays a key role in oncogenesis with the power to control both genetic and epigenetic events in cells. In this review, we discuss the relationship between metabolism and cancer, as part of a larger effort to identify a broad-spectrum of therapeutic approaches. We focus on major alterations in nutrient metabolism and the emerging link between metabolism and epigenetics. Finally, we discuss potential strategies to manipulate metabolism in cancer and tradeoffs that should be considered. More research on the suite of metabolic alterations in cancer holds the potential to discover novel approaches to treat it.
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Spaans SK, Weusthuis RA, van der Oost J, Kengen SWM. NADPH-generating systems in bacteria and archaea. Front Microbiol 2015; 6:742. [PMID: 26284036 PMCID: PMC4518329 DOI: 10.3389/fmicb.2015.00742] [Citation(s) in RCA: 197] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 07/06/2015] [Indexed: 12/22/2022] Open
Abstract
Reduced nicotinamide adenine dinucleotide phosphate (NADPH) is an essential electron donor in all organisms. It provides the reducing power that drives numerous anabolic reactions, including those responsible for the biosynthesis of all major cell components and many products in biotechnology. The efficient synthesis of many of these products, however, is limited by the rate of NADPH regeneration. Hence, a thorough understanding of the reactions involved in the generation of NADPH is required to increase its turnover through rational strain improvement. Traditionally, the main engineering targets for increasing NADPH availability have included the dehydrogenase reactions of the oxidative pentose phosphate pathway and the isocitrate dehydrogenase step of the tricarboxylic acid (TCA) cycle. However, the importance of alternative NADPH-generating reactions has recently become evident. In the current review, the major canonical and non-canonical reactions involved in the production and regeneration of NADPH in prokaryotes are described, and their key enzymes are discussed. In addition, an overview of how different enzymes have been applied to increase NADPH availability and thereby enhance productivity is provided.
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Affiliation(s)
| | - Ruud A. Weusthuis
- Bioprocess Engineering, Wageningen UniversityWageningen, Netherlands
| | - John van der Oost
- Laboratory of Microbiology, Wageningen UniversityWageningen, Netherlands
| | - Servé W. M. Kengen
- Laboratory of Microbiology, Wageningen UniversityWageningen, Netherlands
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20
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Jackson JB, Leung JH, Stout CD, Schurig-Briccio LA, Gennis RB. Review and Hypothesis. New insights into the reaction mechanism of transhydrogenase: Swivelling the dIII component may gate the proton channel. FEBS Lett 2015; 589:2027-33. [PMID: 26143375 DOI: 10.1016/j.febslet.2015.06.027] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2015] [Revised: 06/17/2015] [Accepted: 06/17/2015] [Indexed: 11/26/2022]
Abstract
The membrane protein transhydrogenase in animal mitochondria and bacteria couples reduction of NADP⁺ by NADH to proton translocation. Recent X-ray data on Thermus thermophilus transhydrogenase indicate a significant difference in the orientations of the two dIII components of the enzyme dimer (Leung et al., 2015). The character of the orientation change, and a review of information on the kinetics and thermodynamics of transhydrogenase, indicate that dIII swivelling might assist in the control of proton gating by the redox state of bound NADP⁺/NADPH during enzyme turnover.
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Affiliation(s)
- J Baz Jackson
- School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK.
| | - Josephine H Leung
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92307, USA
| | - Charles D Stout
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92307, USA
| | | | - Robert B Gennis
- Department of Biochemistry, University of Illinois, Urbana, IL 61801, USA
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21
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Fujisawa Y, Napoli E, Wong S, Song G, Yamaguchi R, Matsui T, Nagasaki K, Ogata T, Giulivi C. Impact of a novel homozygous mutation in nicotinamide nucleotide transhydrogenase on mitochondrial DNA integrity in a case of familial glucocorticoid deficiency. BBA CLINICAL 2015; 3:70-78. [PMID: 26309815 PMCID: PMC4545511 DOI: 10.1016/j.bbacli.2014.12.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
BACKGROUND Familial Glucocorticoid Deficiency (FGD) is a rare autosomal recessive disorder that is characterized by isolated glucocorticoid deficiency. Recently, mutations in the gene encoding for the mitochondrial nicotinamide nucleotide transhydrogenase (NNT) have been identified as a causative gene for FGD; however, no NNT activities have been reported in FGD patients carrying NNT mutations. METHODS Clinical, biochemical and molecular analyses of lymphocytes from FDG homozygous and heterozygous carriers for the F215S NNT mutation. RESULTS In this study, we described an FGD-affected Japanese patient carrying a novel NNT homozygous mutation (c.644T>C; F215S) with a significant loss-of-function (NNT activity = 31% of healthy controls) in peripheral blood cells' mitochondria. The NNT activities of the parents, heterozygous for the mutation, were 61% of controls. CONCLUSIONS Our results indicated that (i) mitochondrial biogenesis (citrate synthase activity) and/or mtDNA replication (mtDNA copy number) were affected at ≤60% NNT activity because these parameters were affected in individuals carrying either one or both mutated alleles; and (ii) other outcomes (mtDNA deletions, protein tyrosine nitration, OXPHOS capacity) were affected at ≤30% NNT activity as also observed in murine cerebellar mitochondria from C57BL/6J (NNT-/-) vs. C57BL/6JN (NNT+/+) substrains. GENERAL SIGNIFICANCE By studying a family affected with a novel point mutation in the NNT gene, a gene-dose response was found for various mitochondrial outcomes providing for novel insights into the role of NNT in the maintenance of mtDNA integrity beyond that described for preventing oxidative stress.
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Affiliation(s)
- Yasuko Fujisawa
- Department of Pediatrics, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Eleonora Napoli
- Department of Molecular Biosciences, University of California Davis, Davis, CA 95616, USA
| | - Sarah Wong
- Department of Molecular Biosciences, University of California Davis, Davis, CA 95616, USA
| | - Gyu Song
- Department of Molecular Biosciences, University of California Davis, Davis, CA 95616, USA
| | - Rie Yamaguchi
- Department of Pediatrics, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Toshiharu Matsui
- Department of Pediatrics, Nagaoka Chuo General Hospital, Nagaoka 940-8653, Japan
| | - Keisuke Nagasaki
- Division of Pediatrics, Niigata University Graduate School of Medicine and Dental Sciences, Niigata 951-8122, Japan
| | - Tsutomu Ogata
- Department of Pediatrics, Hamamatsu University School of Medicine, Hamamatsu 431-3192, Japan
| | - Cecilia Giulivi
- Department of Molecular Biosciences, University of California Davis, Davis, CA 95616, USA ; Medical Investigations of Neurodevelopmental Disorders (M. I. N. D.) Institute, University of California Davis, Sacramento, CA 95616
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22
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Yang W, Catalanotti C, Wittkopp TM, Posewitz MC, Grossman AR. Algae after dark: mechanisms to cope with anoxic/hypoxic conditions. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2015; 82:481-503. [PMID: 25752440 DOI: 10.1111/tpj.12823] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Revised: 02/28/2015] [Accepted: 03/03/2015] [Indexed: 06/04/2023]
Abstract
Chlamydomonas reinhardtii is a unicellular, soil-dwelling (and aquatic) green alga that has significant metabolic flexibility for balancing redox equivalents and generating ATP when it experiences hypoxic/anoxic conditions. The diversity of pathways available to ferment sugars is often revealed in mutants in which the activities of specific branches of fermentative metabolism have been eliminated; compensatory pathways that have little activity in parental strains under standard laboratory fermentative conditions are often activated. The ways in which these pathways are regulated and integrated have not been extensively explored. In this review, we primarily discuss the intricacies of dark anoxic metabolism in Chlamydomonas, but also discuss aspects of dark oxic metabolism, the utilization of acetate, and the relatively uncharacterized but critical interactions that link chloroplastic and mitochondrial metabolic networks.
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Affiliation(s)
- Wenqiang Yang
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA
| | - Claudia Catalanotti
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA
| | - Tyler M Wittkopp
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA
- Department of Biology, Stanford University, Stanford, CA, 94305, USA
| | - Matthew C Posewitz
- Department of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO, 80401, USA
| | - Arthur R Grossman
- Department of Plant Biology, Carnegie Institution for Science, Stanford, CA, 94305, USA
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23
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Leung JH, Schurig-Briccio LA, Yamaguchi M, Moeller A, Speir JA, Gennis RB, Stout CD. Structural biology. Division of labor in transhydrogenase by alternating proton translocation and hydride transfer. Science 2015; 347:178-81. [PMID: 25574024 DOI: 10.1126/science.1260451] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
NADPH/NADP(+) (the reduced form of NADP(+)/nicotinamide adenine dinucleotide phosphate) homeostasis is critical for countering oxidative stress in cells. Nicotinamide nucleotide transhydrogenase (TH), a membrane enzyme present in both bacteria and mitochondria, couples the proton motive force to the generation of NADPH. We present the 2.8 Å crystal structure of the transmembrane proton channel domain of TH from Thermus thermophilus and the 6.9 Å crystal structure of the entire enzyme (holo-TH). The membrane domain crystallized as a symmetric dimer, with each protomer containing a putative proton channel. The holo-TH is a highly asymmetric dimer with the NADP(H)-binding domain (dIII) in two different orientations. This unusual arrangement suggests a catalytic mechanism in which the two copies of dIII alternatively function in proton translocation and hydride transfer.
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Affiliation(s)
- Josephine H Leung
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | | | - Mutsuo Yamaguchi
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Arne Moeller
- National Resource for Automated Molecular Microscopy, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Jeffrey A Speir
- National Resource for Automated Molecular Microscopy, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Robert B Gennis
- Department of Biochemistry, University of Illinois, Urbana, IL 61801, USA
| | - Charles D Stout
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
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Abstract
UNLABELLED Creation of lethal and synthetic lethal mutations in an experimental organism is a cornerstone of genetic dissection of gene function, and is related to the concept of an essential gene. Common inbred mouse strains carry background mutations, which can act as genetic modifiers, interfering with the assignment of gene essentiality. The inbred strain C57BL/6J, commonly known as "Black Six", stands out, as it carries a spontaneous homozygous deletion in the nicotinamide nucleotide transhydrogenase (Nnt) gene [GenBank: AH009385.2], resulting in impairment of steroidogenic mitochondria of the adrenal gland, and a multitude of indirect modifier effects, coming from alteration of glucocorticoid-regulated processes. Over time, the popular strain has been used, by means of gene targeting technology, to assign "essential" and "redundant" qualifiers to numerous genes, thus creating an internally consistent "parallel universe" of knowledge. It is unrealistic to suggest phasing-out of this strain, given the scope of shared resources built around it, however, continuing on the road of "strain-unawareness" will result in profound waste of effort, particularly where translational research is concerned. The review analyzes the historical roots of this phenomenon and proposes that building of "parallel universes" should be urgently made visible to a critical reader by obligatory use of unambiguous and persistent tags in publications and databases, such as hypertext links, pointing to a vendor's strain description web page, or to a digital object identifier (d.o.i.) of the original publication, so that any research done exclusively in C57BL/6J, could be easily identified. REVIEWERS This article was reviewed by Dr. Neil Smalheiser and Dr. Miguel Andrade-Navarro.
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Affiliation(s)
- Alexander Kraev
- Charles H, Best Institute, Banting and Best Department of Medical Research, University of Toronto, Toronto, Ontario M5G 1L6, Canada.
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25
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Rogers C, Davis B, Neufer PD, Murphy MP, Anderson EJ, Robidoux J. A transient increase in lipid peroxidation primes preadipocytes for delayed mitochondrial inner membrane permeabilization and ATP depletion during prolonged exposure to fatty acids. Free Radic Biol Med 2014; 67:330-41. [PMID: 24269897 PMCID: PMC3935619 DOI: 10.1016/j.freeradbiomed.2013.11.012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 10/29/2013] [Accepted: 11/12/2013] [Indexed: 12/22/2022]
Abstract
Preadipocytes are periodically subjected to fatty acid (FA) concentrations that are potentially cytotoxic. We tested the hypothesis that prolonged exposure of preadipocytes of human origin to a physiologically relevant mix of FAs leads to mitochondrial inner membrane (MIM) permeabilization and ultimately to mitochondrial crisis. We found that exposure of preadipocytes to FAs led to progressive cyclosporin A-sensitive MIM permeabilization, which in turn caused a reduction in MIM potential, oxygen consumption, and ATP synthetic capacity and, ultimately, death. Additionally, we showed that FAs induce a transient increase in intramitochondrial reactive oxygen species (ROS) and lipid peroxide production, lasting roughly 30 and 120min for the ROS and lipid peroxides, respectively. MIM permeabilization and its deleterious consequences including mitochondrial crisis and cell death were prevented by treating the cells with the mitochondrial FA uptake inhibitor etomoxir, the mitochondrion-selective superoxide and lipid peroxide antioxidants MitoTempo and MitoQ, or the lipid peroxide and reactive carbonyl scavenger l-carnosine. FAs also promoted a delayed oxidative stress phase. However, the beneficial effects of etomoxir, MitoTempo, and l-carnosine were lost by delaying the treatment by 2h, suggesting that the initial phase was sufficient to prime the cells for the delayed MIM permeabilization and mitochondrial crisis. It also suggested that the second ROS production phase is a consequence of this loss in mitochondrial health. Altogether, our data suggest that approaches designed to diminish intramitochondrial ROS or lipid peroxide accumulation, as well as MIM permeabilization, are valid mechanism-based therapeutic avenues to prevent the loss in preadipocyte metabolic fitness associated with prolonged exposure to elevated FA levels.
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Affiliation(s)
- Carlyle Rogers
- Department of Pharmacology and Toxicology, East Carolina University, Greenville, NC 27834, USA
| | - Barbara Davis
- Department of Pharmacology and Toxicology, East Carolina University, Greenville, NC 27834, USA
| | - P Darrell Neufer
- Department of Physiology, East Carolina University, Greenville, NC 27834, USA; Department of Kinesiology, East Carolina University, Greenville, NC 27834, USA; East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC 27834, USA
| | - Michael P Murphy
- MRC Mitochondrial Biology Unit, Wellcome Trust/MRC Building, Cambridge CB2 0XY, UK
| | - Ethan J Anderson
- Department of Pharmacology and Toxicology, East Carolina University, Greenville, NC 27834, USA; Department of Kinesiology, East Carolina University, Greenville, NC 27834, USA; East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC 27834, USA
| | - Jacques Robidoux
- Department of Pharmacology and Toxicology, East Carolina University, Greenville, NC 27834, USA; East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, NC 27834, USA.
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26
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Cheung CYM, Williams TCR, Poolman MG, Fell DA, Ratcliffe RG, Sweetlove LJ. A method for accounting for maintenance costs in flux balance analysis improves the prediction of plant cell metabolic phenotypes under stress conditions. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2013; 75:1050-61. [PMID: 23738527 DOI: 10.1111/tpj.12252] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/03/2013] [Revised: 05/23/2013] [Accepted: 05/30/2013] [Indexed: 05/24/2023]
Abstract
Flux balance models of metabolism generally utilize synthesis of biomass as the main determinant of intracellular fluxes. However, the biomass constraint alone is not sufficient to predict realistic fluxes in central heterotrophic metabolism of plant cells because of the major demand on the energy budget due to transport costs and cell maintenance. This major limitation can be addressed by incorporating transport steps into the metabolic model and by implementing a procedure that uses Pareto optimality analysis to explore the trade-off between ATP and NADPH production for maintenance. This leads to a method for predicting cell maintenance costs on the basis of the measured flux ratio between the oxidative steps of the oxidative pentose phosphate pathway and glycolysis. We show that accounting for transport and maintenance costs substantially improves the accuracy of fluxes predicted from a flux balance model of heterotrophic Arabidopsis cells in culture, irrespective of the objective function used in the analysis. Moreover, when the new method was applied to cells under control, elevated temperature and hyper-osmotic conditions, only elevated temperature led to a substantial increase in cell maintenance costs. It is concluded that the hyper-osmotic conditions tested did not impose a metabolic stress, in as much as the metabolic network is not forced to devote more resources to cell maintenance.
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Affiliation(s)
- C Y Maurice Cheung
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford, OX1 3RB, UK
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Intertissue Differences for the Role of Glutamate Dehydrogenase in Metabolism. Neurochem Res 2013; 39:516-26. [DOI: 10.1007/s11064-013-0998-z] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2012] [Revised: 01/24/2013] [Accepted: 02/01/2013] [Indexed: 11/26/2022]
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Kavitha L, Muniyappan A, Prabhu A, Zdravković S, Jayanthi S, Gopi D. Nano breathers and molecular dynamics simulations in hydrogen-bonded chains. J Biol Phys 2013; 39:15-35. [PMID: 23860832 PMCID: PMC3532661 DOI: 10.1007/s10867-012-9283-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2012] [Accepted: 08/13/2012] [Indexed: 10/27/2022] Open
Abstract
Non-linear localization phenomena in biological lattices have attracted a steadily growing interest and their existence has been predicted in a wide range of physical settings. We investigate the non-linear proton dynamics of a hydrogen-bonded chain in a semi-classical limit using the coherent state method combined with a Holstein-Primakoff bosonic representation. We demonstrate that even a weak inherent discreteness in the hydrogen-bonded (HB) chain may drastically modify the dynamics of the non-linear system, leading to instabilities that have no analog in the continuum limit. We suggest a possible localization mechanism of polarization oscillations of protons in a hydrogen-bonded chain through modulational instability analysis. This mechanism arises due to the neighboring proton-proton interaction and coherent tunneling of protons along hydrogen bonds and/or around heavy atoms. We present a detailed analysis of modulational instability, and highlight the role of the interaction strength of neighboring protons in the process of bioenergy localization. We perform molecular dynamics simulations and demonstrate the existence of nanoscale discrete breather (DB) modes in the hydrogen-bonded chain. These highly localized and long-lived non-linear breather modes may play a functional role in targeted energy transfer in biological systems.
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Affiliation(s)
- L Kavitha
- Department of Physics, Periyar University, Salem, 636 011, India.
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Agarwal AR, Zhao L, Sancheti H, Sundar IK, Rahman I, Cadenas E. Short-term cigarette smoke exposure induces reversible changes in energy metabolism and cellular redox status independent of inflammatory responses in mouse lungs. Am J Physiol Lung Cell Mol Physiol 2012; 303:L889-98. [PMID: 23064950 DOI: 10.1152/ajplung.00219.2012] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Cigarette smoking leads to alteration in cellular redox status, a hallmark in the pathogenesis of chronic obstructive pulmonary disease. This study examines the role of cigarette smoke (CS) exposure in the impairment of energy metabolism and, consequently, mitochondrial dysfunction. Male A/J mice were exposed to CS generated by a smoking machine for 4 or 8 wk. A recovery group was exposed to CS for 8 wk and allowed to recover for 2 wk. Acute CS exposure altered lung glucose metabolism, entailing a decrease in the rate of glycolysis and an increase in the pentose phosphate pathway, as evidenced by altered expression and activity of GAPDH and glucose-6-phosphate dehydrogenase, respectively. Impairment of GAPDH was found to be due to glutathionylation of its catalytic site cysteines. Metabolic changes were associated with changes in cellular and mitochondrial redox status, assessed in terms of pyridine nucleotides and glutathione. CS exposure elicited an upregulation of the expression of complexes II, III, IV, and V and of the activity of complexes II, IV, and V. Microarray analysis of gene expression in mouse lungs after exposure to CS for 8 wk revealed upregulation of a group of genes involved in metabolism, electron transfer chain, oxidative phosphorylation, mitochondrial transport and dynamics, and redox regulation. These changes occurred independently of inflammatory responses. These findings have implications for the early onset of alterations in energy and redox metabolism upon acute lung exposure to CS.
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Affiliation(s)
- Amit R Agarwal
- Pharmacology & Pharmaceutical Sciences, School of Pharmacy, Univ. of Southern California, Los Angeles, CA 90089-9121, USA
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Cardoso AR, Chausse B, da Cunha FM, Luévano-Martínez LA, Marazzi TBM, Pessoa PS, Queliconi BB, Kowaltowski AJ. Mitochondrial compartmentalization of redox processes. Free Radic Biol Med 2012; 52:2201-8. [PMID: 22564526 DOI: 10.1016/j.freeradbiomed.2012.03.008] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Revised: 03/05/2012] [Accepted: 03/06/2012] [Indexed: 12/25/2022]
Abstract
Knowledge of location and intracellular subcompartmentalization is essential for the understanding of redox processes, because oxidants, owing to their reactive nature, must be generated close to the molecules modified in both signaling and damaging processes. Here we discuss known redox characteristics of various mitochondrial microenvironments. Points covered are the locations of mitochondrial oxidant generation, characteristics of antioxidant systems in various mitochondrial compartments, and diffusion characteristics of oxidants in mitochondria. We also review techniques used to measure redox state in mitochondrial subcompartments, antioxidants targeted to mitochondrial subcompartments, and methodological concerns that must be addressed when using these tools.
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The Role of Mitochondrial NADPH-Dependent Isocitrate Dehydrogenase in Cancer Cells. Int J Cell Biol 2012; 2012:273947. [PMID: 22675360 PMCID: PMC3363418 DOI: 10.1155/2012/273947] [Citation(s) in RCA: 77] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 03/19/2012] [Indexed: 02/07/2023] Open
Abstract
Isocitrate dehydrogenase 2 (IDH2) is located in the mitochondrial matrix. IDH2 acts in the forward Krebs cycle as an NADP+-consuming enzyme, providing NADPH for maintenance of the reduced glutathione and peroxiredoxin systems and for self-maintenance by reactivation of cystine-inactivated IDH2 by glutaredoxin 2. In highly respiring cells, the resulting NAD+ accumulation then induces sirtuin-3-mediated activating IDH2 deacetylation, thus increasing its protective function. Reductive carboxylation of 2-oxoglutarate by IDH2 (in the reverse Krebs cycle direction), which consumes NADPH, may follow glutaminolysis of glutamine to 2-oxoglutarate in cancer cells. When the reverse aconitase reaction and citrate efflux are added, this overall “anoxic” glutaminolysis mode may help highly malignant tumors survive aglycemia during hypoxia. Intermittent glycolysis would hypothetically be required to provide ATP. When oxidative phosphorylation is dormant, this mode causes substantial oxidative stress. Arg172 mutants of human IDH2—frequently found with similar mutants of cytosolic IDH1 in grade 2 and 3 gliomas, secondary glioblastomas, and acute myeloid leukemia—catalyze reductive carboxylation of 2-oxoglutarate and reduction to D-2-hydroxyglutarate, which strengthens the neoplastic phenotype by competitive inhibition of histone demethylation and 5-methylcytosine hydroxylation, leading to genome-wide histone and DNA methylation alternations. D-2-hydroxyglutarate also interferes with proline hydroxylation and thus may stabilize hypoxia-induced factor α.
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Jackson JB. A review of the binding-change mechanism for proton-translocating transhydrogenase. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2012; 1817:1839-46. [PMID: 22538293 DOI: 10.1016/j.bbabio.2012.04.006] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2012] [Revised: 04/04/2012] [Accepted: 04/10/2012] [Indexed: 11/17/2022]
Abstract
Proton-translocating transhydrogenase is found in the inner membranes of animal mitochondria, and in the cytoplasmic membranes of many bacteria. It catalyses hydride transfer from NADH to NADP(+) coupled to inward proton translocation. Evidence is reviewed suggesting the enzyme operates by a "binding-change" mechanism. Experiments with Escherichia coli transhydrogenase indicate the enzyme is driven between "open" and "occluded" states by protonation and deprotonation reactions associated with proton translocation. In the open states NADP(+)/NADPH can rapidly associate with, or dissociate from, the enzyme, and hydride transfer is prevented. In the occluded states bound NADP(+)/NADPH cannot dissociate, and hydride transfer is allowed. Crystal structures of a complex of the nucleotide-binding components of Rhodospirillum rubrum transhydrogenase show how hydride transfer is enabled and disabled at appropriate steps in catalysis, and how release of NADP(+)/NADPH is restricted in the occluded state. Thermodynamic and kinetic studies indicate that the equilibrium constant for hydride transfer on the enzyme is elevated as a consequence of the tight binding of NADPH relative to NADP(+). The protonation site in the translocation pathway must face the outside if NADP(+) is bound, the inside if NADPH is bound. Chemical shift changes detected by NMR may show where alterations in protein conformation resulting from NADP(+) reduction are initiated. This article is part of a Special Issue entitled: 17th European Bioenergetics Conference (EBEC 2012).
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Poehlein A, Schmidt S, Kaster AK, Goenrich M, Vollmers J, Thürmer A, Bertsch J, Schuchmann K, Voigt B, Hecker M, Daniel R, Thauer RK, Gottschalk G, Müller V. An ancient pathway combining carbon dioxide fixation with the generation and utilization of a sodium ion gradient for ATP synthesis. PLoS One 2012; 7:e33439. [PMID: 22479398 PMCID: PMC3315566 DOI: 10.1371/journal.pone.0033439] [Citation(s) in RCA: 190] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Accepted: 02/09/2012] [Indexed: 11/18/2022] Open
Abstract
Synthesis of acetate from carbon dioxide and molecular hydrogen is considered to be the first carbon assimilation pathway on earth. It combines carbon dioxide fixation into acetyl-CoA with the production of ATP via an energized cell membrane. How the pathway is coupled with the net synthesis of ATP has been an enigma. The anaerobic, acetogenic bacterium Acetobacterium woodii uses an ancient version of this pathway without cytochromes and quinones. It generates a sodium ion potential across the cell membrane by the sodium-motive ferredoxin:NAD oxidoreductase (Rnf). The genome sequence of A. woodii solves the enigma: it uncovers Rnf as the only ion-motive enzyme coupled to the pathway and unravels a metabolism designed to produce reduced ferredoxin and overcome energetic barriers by virtue of electron-bifurcating, soluble enzymes.
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Affiliation(s)
- Anja Poehlein
- Göttingen Genomics Laboratory, Institute for Microbiology and Genetics, Georg August University, Göttingen, Germany
| | - Silke Schmidt
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt, Germany
| | | | - Meike Goenrich
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - John Vollmers
- Göttingen Genomics Laboratory, Institute for Microbiology and Genetics, Georg August University, Göttingen, Germany
| | - Andrea Thürmer
- Göttingen Genomics Laboratory, Institute for Microbiology and Genetics, Georg August University, Göttingen, Germany
| | - Johannes Bertsch
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt, Germany
| | - Kai Schuchmann
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt, Germany
| | - Birgit Voigt
- Institute for Microbiology, Ernst Moritz Arndt University Greifswald, Greifswald, Germany
| | - Michael Hecker
- Institute for Microbiology, Ernst Moritz Arndt University Greifswald, Greifswald, Germany
| | - Rolf Daniel
- Göttingen Genomics Laboratory, Institute for Microbiology and Genetics, Georg August University, Göttingen, Germany
| | - Rudolf K. Thauer
- Max Planck Institute for Terrestrial Microbiology, Marburg, Germany
| | - Gerhard Gottschalk
- Göttingen Genomics Laboratory, Institute for Microbiology and Genetics, Georg August University, Göttingen, Germany
| | - Volker Müller
- Molecular Microbiology and Bioenergetics, Institute of Molecular Biosciences, Johann Wolfgang Goethe University, Frankfurt, Germany
- * E-mail:
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The C57BL/6J Mouse Strain Background Modifies the Effect of a Mutation in Bcl2l2. G3-GENES GENOMES GENETICS 2012; 2:99-102. [PMID: 22384386 PMCID: PMC3276190 DOI: 10.1534/g3.111.000778] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 11/09/2011] [Indexed: 11/18/2022]
Abstract
Bcl2l2 encodes BCL-W, an antiapoptotic member of the BCL-2 family of proteins. Intercross of Bcl2l2 +/- mice on a mixed C57BL/6J, 129S5 background produces Bcl2l2 -/- animals with the expected frequency. In contrast, intercross of Bcl2l2 +/- mice on a congenic C57BL/6J background produces relatively few live-born Bcl2l2 -/- animals. Genetic modifiers alter the effect of a mutation. C57BL/6J mice (Mus musculus) have a mutant allele of nicotinamide nucleotide transhydrogenase (Nnt) that can act as a modifier. Loss of NNT decreases the concentration of reduced nicotinamide adenine dinucleotide phosphate within the mitochondrial matrix. Nicotinamide adenine dinucleotide phosphate is a cofactor for glutathione reductase, which regenerates reduced glutathione, an important antioxidant. Thus, loss of NNT activity is associated with increased mitochondrial oxidative damage and cellular stress. To determine whether loss of Bcl2l2 -/- mice on the C57BL/6J background was mediated by the Nnt mutation, we outcrossed Bcl2l2 congenic C57BL/6J (Nnt -/-) mice with the closely related C57BL/6JEiJ (Nnt +/+) strain to produce Bcl2l2 +/- ; Nnt +/+ and Bcl2l2 +/- ; Nnt -/- animals. Intercross of Bcl2l2 +/- ; Nnt +/+ mice produced Bcl2l2 -/- with the expected frequency, whereas intercross of Bcl2l2 +/- ; Nnt -/- animals did not. This finding indicates the C57BL/6J strain background, and possibly the Nnt mutation, modifies the Bcl2l2 mutant phenotype. This and previous reports highlight the importance of knowing the genetic composition of mouse strains used in research studies as well as the accurate reporting of mouse strains in the scientific literature.
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Abstract
SIGNIFICANCE Plants produce many small molecules with biomedical potential. Their absorption from foods, metabolism, their effects on physiological and pathological processes, and the mechanisms of action are intensely investigated. Many are known to affect multiple cellular functions. Mitochondria are coming to be recognized as a major target for these compounds, especially redox-active ones, but the mechanisms involved still need clarification. At the same time, frontline research is uncovering the importance of processes involving these organelles for the cell and for an array of physiological and pathological processes. We review the major functions and possible dysfunctions of mitochondria, identify signaling pathways through which plant-derived molecules have an impact, and show how this may be relevant for major pathologies. RECENT ADVANCES Antioxidant, protective effects may arise as a reaction to a low-level pro-oxidant activity, largely taking place at mitochondria. Some plant-derived molecules can activate AMP-dependent kinase, with a consequent upregulation of mitochondrial biogenesis and a potential favorable impact on aging, pathologies like diabetes and neurodegeneration, and on ischemic damage. CRITICAL ISSUES The extrapolation of in vitro results and the verification of paradigms in vivo is a key issue for current research on both plant-derived compounds and mitochondria. The low bioavailability of many of these molecules poses a problem for both the study of their activities and their utilization. FUTURE DIRECTIONS The further clarification of the role of mitochondria in the activities of plant dietary compounds and their metabolites, mitochondrial targeting, the development of analogs and pro-drugs are all topics for promising research.
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Affiliation(s)
- Lucia Biasutto
- CNR Institute of Neuroscience, Department of Experimental Biomedical Sciences, University of Padova, Padova, Italy
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36
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Albracht SPJ, Meijer AJ, Rydström J. Mammalian NADH:ubiquinone oxidoreductase (Complex I) and nicotinamide nucleotide transhydrogenase (Nnt) together regulate the mitochondrial production of H₂O₂--implications for their role in disease, especially cancer. J Bioenerg Biomembr 2011; 43:541-64. [PMID: 21882037 DOI: 10.1007/s10863-011-9381-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 08/03/2011] [Indexed: 12/20/2022]
Abstract
Mammalian NADH:ubiquinone oxidoreductase (Complex I) in the mitochondrial inner membrane catalyzes the oxidation of NADH in the matrix. Excess NADH reduces nine of the ten prosthetic groups of the enzyme in bovine-heart submitochondrial particles with a rate of at least 3,300 s⁻¹. This results in an overall NADH→O₂ rate of ca. 150 s⁻¹. It has long been known that the bovine enzyme also has a specific reaction site for NADPH. At neutral pH excess NADPH reduces only three to four of the prosthetic groups in Complex I with a rate of 40 s⁻¹ at 22 °C. The reducing equivalents remain essentially locked in the enzyme because the overall NADPH→O₂ rate (1.4 s⁻¹) is negligible. The physiological significance of the reaction with NADPH is still unclear. A number of recent developments has revived our thinking about this enigma. We hypothesize that Complex I and the Δp-driven nicotinamide nucleotide transhydrogenase (Nnt) co-operate in an energy-dependent attenuation of the hydrogen-peroxide generation by Complex I. This co-operation is thought to be mediated by the NADPH/NADP⁺ ratio in the vicinity of the NADPH site of Complex I. It is proposed that the specific H₂O₂ production by Complex I, and the attenuation of it, is of importance for apoptosis, autophagy and the survival mechanism of a number of cancers. Verification of this hypothesis may contribute to a better understanding of the regulation of these processes.
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Affiliation(s)
- Simon P J Albracht
- Swammerdam Institute for Life Sciences, University of Amsterdam, Science Park 904, NL-1098 XH, Amsterdam, The Netherlands.
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37
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Kohlmann Y, Pohlmann A, Otto A, Becher D, Cramm R, Lütte S, Schwartz E, Hecker M, Friedrich B. Analyses of soluble and membrane proteomes of Ralstonia eutropha H16 reveal major changes in the protein complement in adaptation to lithoautotrophy. J Proteome Res 2011; 10:2767-76. [PMID: 21561103 DOI: 10.1021/pr101289v] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The soil-dwelling lithoautotrophic bacterium Ralstonia eutropha H16 utilizes hydrogen as the key source of energy during aerobic growth on hydrogen and carbon dioxide. We examined the soluble and membrane protein complements of lithoautotrophically grown cells and compared them to the protein complements of cells grown organoheterotrophically on succinate. (14)N/(15)N-based inverse metabolic labeling in combination with GeLC-MS led to the identification of 1452 proteins, 1174 of which could be quantitated. Far more proteins were found to be more abundant in the lithoautotrophically than in the organoheterotrophically grown cells. In addition to the induction of the key enzymes of hydrogen oxidation and carbon dioxide fixation, we observed several characteristic alterations in the proteome correlated with lithoautotrophic growth. (I) Genes for three terminal oxidases were upregulated. (II) NAD(P) transhydrogenase and enzymes for the accumulation of poly(3-hydroxybutyrate) (PHB) showed increased protein abundance. (III) Lithoautotrophically grown cells were equipped with an enhanced inventory of transport systems. (IV) The expression of cell surface appendages involved in cell movement was markedly increased, while proteins involved in cell adhesion were decreased. Our data show that the hydrogen-based lifestyle of R. eutropha H16 relies on an extensive protein repertoire adapting the organism to the alternative energy and carbon sources.
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Affiliation(s)
- Yvonne Kohlmann
- Institut für Biologie, Humboldt-Universität zu Berlin, 10115 Berlin, Germany
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38
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Leloup C, Casteilla L, Carrière A, Galinier A, Benani A, Carneiro L, Pénicaud L. Balancing mitochondrial redox signaling: a key point in metabolic regulation. Antioxid Redox Signal 2011; 14:519-30. [PMID: 20977349 DOI: 10.1089/ars.2010.3424] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Mitochondrial reactive oxygen species (mROS) have emerged as signaling molecules in physiology primarily as a result of studies of uncoupling mechanisms in mitochondrial respiration. The discovery that this mechanism negatively regulates mROS generation in many cell types has drawn the attention of the scientific community to the pathological consequences of excess mROS production. From reports of the energetic fluxes in cells grown under normal conditions, the hypothesis that mROS are an integrated physiological signal of the metabolic status of the cell has emerged. Here, we consider recent studies that support this point of view in two key nutrient sensors of the body, beta cells and the hypothalamus, which are the main coordinators of endocrine and nervous controls of energy metabolism and adipose tissue, which is of paramount importance in controlling body weight and, therefore, the development of obesity and type 2 diabetes. In this context, finely balanced mROS production may be at the core of proper metabolic maintenance, and unbalanced mROS production, which is largely documented, might be an important trigger of metabolic disorders.
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Affiliation(s)
- Corinne Leloup
- Centre des Sciences du Goût et de l'Alimentation, Centre National de la Recherche Scientifique Unité Mixte de Recherche 6265-Institut National de Recherche Agronomique 1324, Université de Bourgogne, Dijon, France.
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Abstract
In the present chapter, the structures and mechanisms of the major components of mammalian mitochondrial respiratory chains are reviewed. Particular emphasis is placed on the four protein complexes and their cofactors that catalyse the electron transfer pathway between oxidation of NADH and succinate and the reduction of oxygen to water. Current ideas are reviewed of how these electron transfer reactions are coupled to formation of the proton and charge gradient across the inner mitochondrial membrane that is used to drive ATP synthesis. Additional respiratory components that are found in mammalian and plant, fungal and algal mitochondria are also reviewed.
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40
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Queliconi BB, Wojtovich AP, Nadtochiy SM, Kowaltowski AJ, Brookes PS. Redox regulation of the mitochondrial K(ATP) channel in cardioprotection. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1813:1309-15. [PMID: 21094666 DOI: 10.1016/j.bbamcr.2010.11.005] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 10/05/2010] [Accepted: 11/11/2010] [Indexed: 12/12/2022]
Abstract
The mitochondrial ATP-sensitive potassium channel (mK(ATP)) is important in the protective mechanism of ischemic preconditioning (IPC). The channel is reportedly sensitive to reactive oxygen and nitrogen species, and the aim of this study was to compare such species in parallel, to build a more comprehensive picture of mK(ATP) regulation. mK(ATP) activity was measured by both osmotic swelling and Tl(+) flux assays, in isolated rat heart mitochondria. An isolated adult rat cardiomyocyte model of ischemia-reperfusion (IR) injury was also used to determine the role of mK(ATP) in cardioprotection by nitroxyl. Key findings were as follows: (i) mK(ATP) was activated by O(2)(-) and H(2)O(2) but not other peroxides. (ii) mK(ATP) was inhibited by NADPH. (iii) mK(ATP) was activated by S-nitrosothiols, nitroxyl, and nitrolinoleate. The latter two species also inhibited mitochondrial complex II. (iv) Nitroxyl protected cardiomyocytes against IR injury in an mK(ATP)-dependent manner. Overall, these results suggest that the mK(ATP) channel is activated by specific reactive oxygen and nitrogen species, and inhibited by NADPH. The redox modulation of mK(ATP) may be an underlying mechanism for its regulation in the context of IPC. This article is part of a Special Issue entitled: Mitochondria and Cardioprotection.
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Affiliation(s)
- Bruno B Queliconi
- Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, São Paulo, SP, Brazil
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41
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Huxley L, Quirk PG, Cotton NPJ, White SA, Jackson JB. The specificity of proton-translocating transhydrogenase for nicotinamide nucleotides. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1807:85-94. [PMID: 20732298 DOI: 10.1016/j.bbabio.2010.08.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Accepted: 08/10/2010] [Indexed: 11/29/2022]
Abstract
In its forward direction, transhydrogenase couples the reduction of NADP(+) by NADH to the outward translocation of protons across the membrane of bacteria and animal mitochondria. The enzyme has three components: dI and dIII protrude from the membrane and dII spans the membrane. Hydride transfer takes place between nucleotides bound to dI and dIII. Studies on the kinetics of a lag phase at the onset of a "cyclic reaction" catalysed by complexes of the dI and dIII components of transhydrogenase from Rhodospirillum rubrum, and on the kinetics of fluorescence changes associated with nucleotide binding, reveal two features. Firstly, the binding of NADP(+) and NADPH to dIII is extremely slow, and is probably limited by the conversion of the occluded to the open state of the complex. Secondly, dIII can also bind NAD(+) and NADH. Extrapolating to the intact enzyme this binding to the "wrong" site could lead to slip: proton translocation without change in the nucleotide redox state, which would have important consequences for bacterial and mitochondrial metabolism.
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Affiliation(s)
- Lucinda Huxley
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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42
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Treberg JR, Brosnan ME, Brosnan JT. The simultaneous determination of NAD(H) and NADP(H) utilization by glutamate dehydrogenase. Mol Cell Biochem 2010; 344:253-9. [PMID: 20697932 DOI: 10.1007/s11010-010-0549-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2010] [Accepted: 07/23/2010] [Indexed: 10/19/2022]
Abstract
Glutamate dehydrogenase (GDH) from vertebrates is unusual among NAD(P)H-dependent dehydrogenases in that it can use either NAD(H) or NADP(H) as cofactor. In this study, we measure the rate of cofactor utilization by bovine GDH when both cofactors are present. Methods for both reaction directions were developed, and for the first time, to our knowledge, the GDH activity has been simultaneously studied in the presence of both NAD(H) and NADP(H). Our data indicate that NADP(H) has inhibitory effects on the rate of NAD(H) utilization by GDH, a characteristic of GDH not previously recognized. The response of GDH to allosteric activators in the presence of NAD(H) and NADP(H) suggests that ADP and leucine moderate much of the inhibitory effect of NADP(H) on the utilization of NAD(H). These results illustrate that simple assumptions of cofactor preference by mammalian GDH are incomplete without an appreciation of allosteric effects when both cofactors are simultaneously present.
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Affiliation(s)
- Jason R Treberg
- Department of Biochemistry, Memorial University of Newfoundland, St. John's, NL, Canada.
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43
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NADP+ reduction with reduced ferredoxin and NADP+ reduction with NADH are coupled via an electron-bifurcating enzyme complex in Clostridium kluyveri. J Bacteriol 2010; 192:5115-23. [PMID: 20675474 DOI: 10.1128/jb.00612-10] [Citation(s) in RCA: 162] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
It was recently found that the cytoplasmic butyryl-coenzyme A (butyryl-CoA) dehydrogenase-EtfAB complex from Clostridium kluyveri couples the exergonic reduction of crotonyl-CoA to butyryl-CoA with NADH and the endergonic reduction of ferredoxin with NADH via flavin-based electron bifurcation. We report here on a second cytoplasmic enzyme complex in C. kluyveri capable of energetic coupling via this novel mechanism. It was found that the purified iron-sulfur flavoprotein complex NfnAB couples the exergonic reduction of NADP+ with reduced ferredoxin (Fdred) and the endergonic reduction of NADP+ with NADH in a reversible reaction: Fdred2-+NADH+2 NADP++H+=Fdox+NAD++2 NADPH. The role of this energy-converting enzyme complex in the ethanol-acetate fermentation of C. kluyveri is discussed.
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44
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Sheeran FL, Rydström J, Shakhparonov MI, Pestov NB, Pepe S. Diminished NADPH transhydrogenase activity and mitochondrial redox regulation in human failing myocardium. BIOCHIMICA ET BIOPHYSICA ACTA-BIOENERGETICS 2010; 1797:1138-48. [PMID: 20388492 DOI: 10.1016/j.bbabio.2010.04.002] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 11/15/2009] [Revised: 03/30/2010] [Accepted: 04/05/2010] [Indexed: 11/28/2022]
Abstract
Although the functional role of nicotinamide nucleotide transhydrogenase (Nnt) remains to be fully elucidated, there is strong evidence that Nnt plays a critical part in mitochondrial metabolism by maintaining a high NADPH-dependent GSH/GSSG ratio, and thus the control of cellular oxidative stress. Using real-time PCR, spectrophotometric and western blotting techniques, we sought to determine the presence, abundance and activity level of Nnt in human heart tissues and to discern whether these are altered in chronic severe heart failure. Left ventricular levels of the NNT gene and protein expression did not differ significantly between the non-failing donor (NF) and heart failure (HF) group. Notably, compared to NF, Nnt activity rates in the HF group were 18% lower, which coincided with significantly higher levels of oxidized glutathione, lower glutathione reductase activity, lower NADPH and a lower GSH/GSSG ratio. In the failing human heart a partial loss of Nnt activity adversely impacts NADPH-dependent enzymes and the capacity to maintain membrane potential, thus contributing to a decline in bioenergetic capacity, redox regulation and antioxidant defense, exacerbating oxidative damage to cellular proteins.
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Affiliation(s)
- Freya L Sheeran
- Department of Surgery, Monash University Faculty of Medicine, Alfred Hospital, Melbourne, Australia
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45
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Wittig I, Beckhaus T, Wumaier Z, Karas M, Schägger H. Mass estimation of native proteins by blue native electrophoresis: principles and practical hints. Mol Cell Proteomics 2010; 9:2149-61. [PMID: 20173216 DOI: 10.1074/mcp.m900526-mcp200] [Citation(s) in RCA: 100] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Blue native electrophoresis is one of the most popular techniques for mass estimation of native membrane proteins, but the use of non-optimal mass markers and acrylamide gels can compromise accuracy and reliability of the results. We present short protocols taking 10-30 min to prepare optimal sets of membrane protein markers from chicken, rat, mouse, and bovine heart. Especially heart materials from local supermarkets or butcher's shops, e.g. chicken or bovine heart, are ideal sources of high mass membrane protein standards. Considerable discrepancies between the migration behavior of membrane and soluble markers suggest using membrane protein markers for mass estimation of membrane proteins. Soluble standard proteins can be used, with some limitations, when soluble proteins are the focus. Principles and general rules for the determination of mass and oligomeric state of native membrane and soluble proteins are elaborated, and potential pitfalls are discussed.
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Affiliation(s)
- Ilka Wittig
- Molecular Bioenergetics, Medical School, Goethe-Universität Frankfurt, Theodor-Stern-Kai 7, Haus 26, D-60590 Frankfurt am Main, Germany
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Seifert EL, Estey C, Xuan JY, Harper ME. Electron transport chain-dependent and -independent mechanisms of mitochondrial H2O2 emission during long-chain fatty acid oxidation. J Biol Chem 2009; 285:5748-58. [PMID: 20032466 DOI: 10.1074/jbc.m109.026203] [Citation(s) in RCA: 191] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Oxidative stress in skeletal muscle is a hallmark of various pathophysiologic states that also feature increased reliance on long-chain fatty acid (LCFA) substrate, such as insulin resistance and exercise. However, little is known about the mechanistic basis of the LCFA-induced reactive oxygen species (ROS) burden in intact mitochondria, and elucidation of this mechanistic basis was the goal of this study. Specific aims were to determine the extent to which LCFA catabolism is associated with ROS production and to gain mechanistic insights into the associated ROS production. Because intermediates and by-products of LCFA catabolism may interfere with antioxidant mechanisms, we predicted that ROS formation during LCFA catabolism reflects a complex process involving multiple sites of ROS production as well as modified mitochondrial function. Thus, we utilized several complementary approaches to probe the underlying mechanism(s). Using skeletal muscle mitochondria, our findings indicate that even a low supply of LCFA is associated with ROS formation in excess of that generated by NADH-linked substrates. Moreover, ROS production was evident across the physiologic range of membrane potential and was relatively insensitive to membrane potential changes. Determinations of topology and membrane potential as well as use of inhibitors revealed complex III and the electron transfer flavoprotein (ETF) and ETF-oxidoreductase, as likely sites of ROS production. Finally, ROS production was sensitive to matrix levels of LCFA catabolic intermediates, indicating that mitochondrial export of LCFA catabolic intermediates can play a role in determining ROS levels.
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Affiliation(s)
- Erin L Seifert
- Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa, Ontario K1H 8M5, Canada
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Pestov NB, Shakhparonov MI. The effect of ablation of the gene for H+-transporting NAD/NADP transhydrogenase on the life spans of nematodes and mammals. RUSSIAN JOURNAL OF BIOORGANIC CHEMISTRY 2009; 35:681-5. [DOI: 10.1134/s1068162009050124] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Insulin secretion from beta-cells is affected by deletion of nicotinamide nucleotide transhydrogenase. Methods Enzymol 2009; 457:451-80. [PMID: 19426883 DOI: 10.1016/s0076-6879(09)05025-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/29/2023]
Abstract
Nicotinamide nucleotide transhydrogenase (NNT) is an inner mitochondrial membrane transmembrane protein involved in regenerating NADPH, coupled with proton translocation across the inner membrane. We have shown that a defect in Nnt function in the mouse, and specifically within the beta-cell, leads to a reduction in insulin secretion. This chapter describes methods for examining Nnt function in the mouse. This includes generating in vivo models with point mutations and expression of Nnt by transgenesis, and making in vitro models, by silencing of gene expression. In addition, techniques are described to measure insulin secretion, calcium and hydrogen peroxide concentrations, membrane potential, and NNT activity. These approaches and techniques can also be applied to other genes of interest.
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