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12 pages, 4302 KiB

Open AccessArticle

Reduction of Hydrogen Peroxide by Human Mitochondrial Amidoxime Reducing Component Enzymes

by Sophia Rixen, Patrick M. Indorf, Christian Kubitza, Michel A. Struwe, Cathrin Klopp, Axel J. Scheidig, Thomas Kunze and Bernd Clement

Molecules 2023, 28(17), 6384; https://doi.org/10.3390/molecules28176384 - 31 Aug 2023

Cited by 1 | Viewed by 921

Abstract

The mitochondrial amidoxime reducing component (mARC) is a human molybdoenzyme known to catalyze the reduction of various N-oxygenated substrates. The physiological function of mARC enzymes, however, remains unknown. In this study, we examine the reduction of hydrogen peroxide (H₂O₂ [...] Read more.

The mitochondrial amidoxime reducing component (mARC) is a human molybdoenzyme known to catalyze the reduction of various N-oxygenated substrates. The physiological function of mARC enzymes, however, remains unknown. In this study, we examine the reduction of hydrogen peroxide (H₂O₂) by the human mARC1 and mARC2 enzymes. Furthermore, we demonstrate an increased sensitivity toward H₂O₂ for HEK-293T cells with an MTARC1 knockout, which implies a role of mARC enzymes in the cellular response to oxidative stress. H₂O₂ is a reactive oxygen species (ROS) formed in all living cells involved in many physiological processes. Furthermore, H₂O₂ constitutes the first mARC substrate without a nitrogen–oxygen bond, implying that mARC enzymes may have a substrate spectrum going beyond the previously examined N-oxygenated compounds. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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13 pages, 1986 KiB

Open AccessArticle

Studies Relevant to the Functional Model of Mo-Cu CODH: In Situ Reactions of Cu(I)-L Complexes with Mo(VI) and Synthesis of Stable Structurally Characterized Heterotetranuclear Mo^VI₂Cu^I₂ Complex

by Umesh I. Kaluarachchige Don, Ahmad S. Almaat, Cassandra L. Ward and Stanislav Groysman

Molecules 2023, 28(8), 3644; https://doi.org/10.3390/molecules28083644 - 21 Apr 2023

Cited by 2 | Viewed by 2084

Abstract

In this study, we report the synthesis, characterization, and reactions of Cu(I) complexes of the general form Cu(L)(LigH₂) (LigH₂ = xanthene-based heterodinucleating ligand (E)-3-(((5-(bis(pyridin-2-ylmethyl)amino)-2,7-di-tert-butyl-9,9-dimethyl-9H-xanthen-4-yl)imino)methyl)benzene-1,2-diol); L = PMe₃, PPh₃, CN(2,6-Me₂C₆H₃)). New [...] Read more.

In this study, we report the synthesis, characterization, and reactions of Cu(I) complexes of the general form Cu(L)(LigH₂) (LigH₂ = xanthene-based heterodinucleating ligand (E)-3-(((5-(bis(pyridin-2-ylmethyl)amino)-2,7-di-tert-butyl-9,9-dimethyl-9H-xanthen-4-yl)imino)methyl)benzene-1,2-diol); L = PMe₃, PPh₃, CN(2,6-Me₂C₆H₃)). New complexes [Cu(PMe₃)(LigH₂)] and [CuCN(2,6-Me₂C₆H₃)(LigH₂)] were synthesized by treating [Cu(LigH₂)](PF₆) with trimethylphosphine and 2,6-dimethylphenyl isocyanide, respectively. These complexes were characterized by multinuclear NMR spectroscopy, IR spectroscopy, high-resolution mass spectrometry (HRMS), and X-ray crystallography. In contrast, attempted reactions of [Cu(LigH₂)](PF₆) with cyanide or styrene failed to produce isolable crystalline products. Next, the reactivity of these and previously synthesized Cu(I) phosphine and isocyanide complexes with molybdate was interrogated. IR (for isocyanide) and ³¹P NMR (for PPh₃/PMe₃) spectroscopy demonstrates the lack of oxidation reactivity. We also describe herein the first example of a structurally characterized multinuclear complex combining both Mo(VI) and Cu(I) metal ions within the same system. The heterobimetallic tetranuclear complex [Cu₂Mo₂O₄(μ₂-O)(Lig)₂]·HOSiPh₃ was obtained by the reaction of the silylated Mo(VI) precursor (Et₄N)(MoO₃(OSiPh₃)) with LigH₂, followed by the addition of [Cu(NCMe)₄](PF₆). This complex was characterized by NMR spectroscopy, high-resolution mass spectrometry, and X-ray crystallography. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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25 pages, 2700 KiB

Open AccessArticle

The Mechanism of Metal-Containing Formate Dehydrogenases Revisited: The Formation of Bicarbonate as Product Intermediate Provides Evidence for an Oxygen Atom Transfer Mechanism

by Hemant Kumar, Maryam Khosraneh, Siva S. M. Bandaru, Carola Schulzke and Silke Leimkühler

Molecules 2023, 28(4), 1537; https://doi.org/10.3390/molecules28041537 - 5 Feb 2023

Cited by 6 | Viewed by 2316

Abstract

Mo/W-containing formate dehydrogenases (FDH) catalyzed the reversible oxidation of formate to carbon dioxide at their molybdenum or tungsten active sites. While in the reaction of formate oxidation, the product is CO₂, which exits the active site via a hydrophobic channel; bicarbonate [...] Read more.

Mo/W-containing formate dehydrogenases (FDH) catalyzed the reversible oxidation of formate to carbon dioxide at their molybdenum or tungsten active sites. While in the reaction of formate oxidation, the product is CO₂, which exits the active site via a hydrophobic channel; bicarbonate is formed as the first intermediate during the reaction at the active site. Other than what has been previously reported, bicarbonate is formed after an oxygen atom transfer reaction, transferring the oxygen from water to formate and a subsequent proton-coupled electron transfer or hydride transfer reaction involving the sulfido ligand as acceptor. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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Review

Jump to: Research

14 pages, 2208 KiB

Open AccessReview

The Mechanisms of Molybdate Distribution and Homeostasis with Special Focus on the Model Plant Arabidopsis thaliana

by Jan-Niklas Weber, Rieke Minner-Meinen and David Kaufholdt

Molecules 2024, 29(1), 40; https://doi.org/10.3390/molecules29010040 - 20 Dec 2023

Viewed by 976

Abstract

This review article deals with the pathways of cellular and global molybdate distribution in plants, especially with a full overview for the model plant Arabidopsis thaliana. In its oxidized state as bioavailable molybdate, molybdenum can be absorbed from the environment. Especially in [...] Read more.

This review article deals with the pathways of cellular and global molybdate distribution in plants, especially with a full overview for the model plant Arabidopsis thaliana. In its oxidized state as bioavailable molybdate, molybdenum can be absorbed from the environment. Especially in higher plants, molybdenum is indispensable as part of the molybdenum cofactor (Moco), which is responsible for functionality as a prosthetic group in a variety of essential enzymes like nitrate reductase and sulfite oxidase. Therefore, plants need mechanisms for molybdate import and transport within the organism, which are accomplished via high-affinity molybdate transporter (MOT) localized in different cells and membranes. Two different MOT families were identified. Legumes like Glycine max or Medicago truncatula have an especially increased number of MOT1 family members for supplying their symbionts with molybdate for nitrogenase activity. In Arabidopsis thaliana especially, the complete pathway followed by molybdate through the plant is traceable. Not only the uptake from soil by MOT1.1 and its distribution to leaves, flowers, and seeds by MOT2-family members was identified, but also that inside the cell. the transport trough the cytoplasm and the vacuolar storage mechanisms depending on glutathione were described. Finally, supplying the Moco biosynthesis complex by MOT1.2 and MOT2.1 was demonstrated. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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21 pages, 3503 KiB

Open AccessReview

On the Shoulders of Giants—Reaching for Nitrogenase

by Oliver Einsle

Molecules 2023, 28(24), 7959; https://doi.org/10.3390/molecules28247959 - 5 Dec 2023

Viewed by 1685

Abstract

Only a single enzyme system—nitrogenase—carries out the conversion of atmospheric N₂ into bioavailable ammonium, an essential prerequisite for all organismic life. The reduction of this inert substrate at ambient conditions poses unique catalytic challenges that strain our mechanistic understanding even after decades [...] Read more.

Only a single enzyme system—nitrogenase—carries out the conversion of atmospheric N₂ into bioavailable ammonium, an essential prerequisite for all organismic life. The reduction of this inert substrate at ambient conditions poses unique catalytic challenges that strain our mechanistic understanding even after decades of intense research. Structural biology has added its part to this greater tapestry, and in this review, I provide a personal (and highly biased) summary of the parts of the story to which I had the privilege to contribute. It focuses on the crystallographic analysis of the three isoforms of nitrogenases at high resolution and the binding of ligands and inhibitors to the active-site cofactors of the enzyme. In conjunction with the wealth of available biochemical, biophysical, and spectroscopic data on the protein, this has led us to a mechanistic hypothesis based on an elementary mechanism of repetitive hydride formation and insertion. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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25 pages, 9787 KiB

Open AccessReview

Nitrogenase beyond the Resting State: A Structural Perspective

by Rebeccah A. Warmack and Douglas C. Rees

Molecules 2023, 28(24), 7952; https://doi.org/10.3390/molecules28247952 - 5 Dec 2023

Cited by 1 | Viewed by 1434

Abstract

Nitrogenases have the remarkable ability to catalyze the reduction of dinitrogen to ammonia under physiological conditions. How does this happen? The current view of the nitrogenase mechanism focuses on the role of hydrides, the binding of dinitrogen in a reductive elimination process coupled [...] Read more.

Nitrogenases have the remarkable ability to catalyze the reduction of dinitrogen to ammonia under physiological conditions. How does this happen? The current view of the nitrogenase mechanism focuses on the role of hydrides, the binding of dinitrogen in a reductive elimination process coupled to loss of dihydrogen, and the binding of substrates to a binuclear site on the active site cofactor. This review focuses on recent experimental characterizations of turnover relevant forms of the enzyme determined by cryo-electron microscopy and other approaches, and comparison of these forms to the resting state enzyme and the broader family of iron sulfur clusters. Emerging themes include the following: (i) The obligatory coupling of protein and electron transfers does not occur in synthetic and small-molecule iron–sulfur clusters. The coupling of these processes in nitrogenase suggests that they may involve unique features of the cofactor, such as hydride formation on the trigonal prismatic arrangement of irons, protonation of belt sulfurs, and/or protonation of the interstitial carbon. (ii) Both the active site cofactor and protein are dynamic under turnover conditions; the changes are such that more highly reduced forms may differ in key ways from the resting-state structure. Homocitrate appears to play a key role in coupling cofactor and protein dynamics. (iii) Structural asymmetries are observed in nitrogenase under turnover-relevant conditions by cryo-electron microscopy, although the mechanistic relevance of these states (such as half-of-sites reactivity) remains to be established. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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34 pages, 7831 KiB

Open AccessReview

Advancing Our Understanding of Pyranopterin-Dithiolene Contributions to Moco Enzyme Catalysis

by Sharon J. Nieter Burgmayer and Martin L. Kirk

Molecules 2023, 28(22), 7456; https://doi.org/10.3390/molecules28227456 - 7 Nov 2023

Cited by 2 | Viewed by 1331

Abstract

The pyranopterin dithiolene ligand is remarkable in terms of its geometric and electronic structure and is uniquely found in mononuclear molybdenum and tungsten enzymes. The pyranopterin dithiolene is found coordinated to the metal ion, deeply buried within the protein, and non-covalently attached to [...] Read more.

The pyranopterin dithiolene ligand is remarkable in terms of its geometric and electronic structure and is uniquely found in mononuclear molybdenum and tungsten enzymes. The pyranopterin dithiolene is found coordinated to the metal ion, deeply buried within the protein, and non-covalently attached to the protein via an extensive hydrogen bonding network that is enzyme-specific. However, the function of pyranopterin dithiolene in enzymatic catalysis has been difficult to determine. This focused account aims to provide an overview of what has been learned from the study of pyranopterin dithiolene model complexes of molybdenum and how these results relate to the enzyme systems. This work begins with a summary of what is known about the pyranopterin dithiolene ligand in the enzymes. We then introduce the development of inorganic small molecule complexes that model aspects of a coordinated pyranopterin dithiolene and discuss the results of detailed physical studies of the models by electronic absorption, resonance Raman, X-ray absorption and NMR spectroscopies, cyclic voltammetry, X-ray crystallography, and chemical reactivity. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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18 pages, 7578 KiB

Open AccessReview

Making Moco: A Personal History

by Sharon J. Nieter Burgmayer

Molecules 2023, 28(21), 7296; https://doi.org/10.3390/molecules28217296 - 27 Oct 2023

Viewed by 892

Abstract

This contribution describes the path of my nearly forty-year quest to understand the special ligand coordinated to molybdenum and tungsten ions in their respective enzymes. Through this quest, I aimed to discover why nature did not simply use a methyl group on the [...] Read more.

This contribution describes the path of my nearly forty-year quest to understand the special ligand coordinated to molybdenum and tungsten ions in their respective enzymes. Through this quest, I aimed to discover why nature did not simply use a methyl group on the dithiolene that chelates Mo and W but instead chose a complicated pyranopterin. My journey sought answers through the synthesis of model Mo compounds that allowed systematic investigations of the interactions between molybdenum and pterin and molybdenum and pterin-dithiolene and revealed special features of the pyranopterin dithiolene chelate bound to molybdenum. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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26 pages, 1320 KiB

Open AccessReview

History of Maturation of Prokaryotic Molybdoenzymes—A Personal View

by Axel Magalon

Molecules 2023, 28(20), 7195; https://doi.org/10.3390/molecules28207195 - 20 Oct 2023

Viewed by 1045

Abstract

In prokaryotes, the role of Mo/W enzymes in physiology and bioenergetics is widely recognized. It is worth noting that the most diverse family of Mo/W enzymes is exclusive to prokaryotes, with the probable existence of several of them from the earliest forms of [...] Read more.

In prokaryotes, the role of Mo/W enzymes in physiology and bioenergetics is widely recognized. It is worth noting that the most diverse family of Mo/W enzymes is exclusive to prokaryotes, with the probable existence of several of them from the earliest forms of life on Earth. The structural organization of these enzymes, which often include additional redox centers, is as diverse as ever, as is their cellular localization. The most notable observation is the involvement of dedicated chaperones assisting with the assembly and acquisition of the metal centers, including Mo/W-bisPGD, one of the largest organic cofactors in nature. This review seeks to provide a new understanding and a unified model of Mo/W enzyme maturation. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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19 pages, 3426 KiB

Open AccessReview

The History of Animal and Plant Sulfite Oxidase—A Personal View

by Ralf R. Mendel and Günter Schwarz

Molecules 2023, 28(19), 6998; https://doi.org/10.3390/molecules28196998 - 9 Oct 2023

Cited by 1 | Viewed by 1423

Abstract

Sulfite oxidase is one of five molybdenum-containing enzymes known in eukaryotes where it catalyzes the oxidation of sulfite to sulfate. This review covers the history of sulfite oxidase research starting out with the early years of its discovery as a hepatic mitochondrial enzyme [...] Read more.

Sulfite oxidase is one of five molybdenum-containing enzymes known in eukaryotes where it catalyzes the oxidation of sulfite to sulfate. This review covers the history of sulfite oxidase research starting out with the early years of its discovery as a hepatic mitochondrial enzyme in vertebrates, leading to basic biochemical and structural properties that have inspired research for decades. A personal view on sulfite oxidase in plants, that sulfates are assimilated for their de novo synthesis of cysteine, is presented by Ralf Mendel with numerous unexpected findings and unique properties of this single-cofactor sulfite oxidase localized to peroxisomes. Guenter Schwarz connects his research to sulfite oxidase via its deficiency in humans, demonstrating its unique role amongst all molybdenum enzymes in humans. In essence, in both the plant and animal kingdoms, sulfite oxidase represents an important player in redox regulation, signaling and metabolism, thereby connecting sulfur and nitrogen metabolism in multiple ways. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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23 pages, 4312 KiB

Open AccessReview

Bringing Nitric Oxide to the Molybdenum World—A Personal Perspective

by Luisa B. Maia

Molecules 2023, 28(15), 5819; https://doi.org/10.3390/molecules28155819 - 2 Aug 2023

Cited by 1 | Viewed by 1235

Abstract

Molybdenum-containing enzymes of the xanthine oxidase (XO) family are well known to catalyse oxygen atom transfer reactions, with the great majority of the characterised enzymes catalysing the insertion of an oxygen atom into the substrate. Although some family members are known to catalyse [...] Read more.

Molybdenum-containing enzymes of the xanthine oxidase (XO) family are well known to catalyse oxygen atom transfer reactions, with the great majority of the characterised enzymes catalysing the insertion of an oxygen atom into the substrate. Although some family members are known to catalyse the “reverse” reaction, the capability to abstract an oxygen atom from the substrate molecule is not generally recognised for these enzymes. Hence, it was with surprise and scepticism that the “molybdenum community” noticed the reports on the mammalian XO capability to catalyse the oxygen atom abstraction of nitrite to form nitric oxide (NO). The lack of precedent for a molybdenum- (or tungsten) containing nitrite reductase on the nitrogen biogeochemical cycle contributed also to the scepticism. It took several kinetic, spectroscopic and mechanistic studies on enzymes of the XO family and also of sulfite oxidase and DMSO reductase families to finally have wide recognition of the molybdoenzymes’ ability to form NO from nitrite. Herein, integrated in a collection of “personal views” edited by Professor Ralf Mendel, is an overview of my personal journey on the XO and aldehyde oxidase-catalysed nitrite reduction to NO. The main research findings and the path followed to establish XO and AO as competent nitrite reductases are reviewed. The evidence suggesting that these enzymes are probable players of the mammalian NO metabolism is also discussed. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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13 pages, 2702 KiB

Open AccessReview

Metal-Containing Formate Dehydrogenases, a Personal View

by Silke Leimkühler

Molecules 2023, 28(14), 5338; https://doi.org/10.3390/molecules28145338 - 11 Jul 2023

Cited by 2 | Viewed by 1457

Abstract

Mo/W-containing formate dehydrogenases (FDH) catalyzes the reversible oxidation of formate to carbon dioxide at their molybdenum or tungsten active sites. The metal-containing FDHs are members of the dimethylsulfoxide reductase family of mononuclear molybdenum cofactor (Moco)- or tungsten cofactor (Wco)-containing enzymes. In these enzymes, [...] Read more.

Mo/W-containing formate dehydrogenases (FDH) catalyzes the reversible oxidation of formate to carbon dioxide at their molybdenum or tungsten active sites. The metal-containing FDHs are members of the dimethylsulfoxide reductase family of mononuclear molybdenum cofactor (Moco)- or tungsten cofactor (Wco)-containing enzymes. In these enzymes, the active site in the oxidized state comprises a Mo or W atom present in the bis-Moco, which is coordinated by the two dithiolene groups from the two MGD moieties, a protein-derived SeCys or Cys, and a sixth ligand that is now accepted as being a sulfido group. SeCys-containing enzymes have a generally higher turnover number than Cys-containing enzymes. The analogous chemical properties of W and Mo, the similar active sites of W- and Mo-containing enzymes, and the fact that W can replace Mo in some enzymes have led to the conclusion that Mo- and W-containing FDHs have the same reaction mechanism. Details of the catalytic mechanism of metal-containing formate dehydrogenases are still not completely understood and have been discussed here. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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14 pages, 1913 KiB

Open AccessReview

The History of mARC

by Bernd Clement and Michel A. Struwe

Molecules 2023, 28(12), 4713; https://doi.org/10.3390/molecules28124713 - 12 Jun 2023

Cited by 7 | Viewed by 1885

Abstract

The mitochondrial amidoxime-reducing component (mARC) is the most recently discovered molybdoenzyme in humans after sulfite oxidase, xanthine oxidase and aldehyde oxidase. Here, the timeline of mARC’s discovery is briefly described. The story begins with investigations into N-oxidation of pharmaceutical drugs and model [...] Read more.

The mitochondrial amidoxime-reducing component (mARC) is the most recently discovered molybdoenzyme in humans after sulfite oxidase, xanthine oxidase and aldehyde oxidase. Here, the timeline of mARC’s discovery is briefly described. The story begins with investigations into N-oxidation of pharmaceutical drugs and model compounds. Many compounds are N-oxidized extensively in vitro, but it turned out that a previously unknown enzyme catalyzes the retroreduction of the N-oxygenated products in vivo. After many years, the molybdoenzyme mARC could finally be isolated and identified in 2006. mARC is an important drug-metabolizing enzyme and N-reduction by mARC has been exploited very successfully for prodrug strategies, that allow oral administration of otherwise poorly bioavailable therapeutic drugs. Recently, it was demonstrated that mARC is a key factor in lipid metabolism and likely involved in the pathogenesis of non-alcoholic fatty liver disease (NAFLD). The exact link between mARC and lipid metabolism is not yet fully understood. Regardless, many now consider mARC a potential drug target for the prevention or treatment of liver diseases. This article focusses on discoveries related to mammalian mARC enzymes. mARC homologues have been studied in algae, plants and bacteria. These will not be discussed extensively here. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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15 pages, 2093 KiB

Open AccessReview

XDH and XO Research and Drug Discovery—Personal History

by Takeshi Nishino

Molecules 2023, 28(11), 4440; https://doi.org/10.3390/molecules28114440 - 30 May 2023

Cited by 2 | Viewed by 3486

Abstract

The author will outline the research history of the main issues addressed in this paper. The author has worked on this research himself. XDH, which is responsible for purine degradation, is present in various organisms. However, conversion to XO only occurs in mammals. [...] Read more.

The author will outline the research history of the main issues addressed in this paper. The author has worked on this research himself. XDH, which is responsible for purine degradation, is present in various organisms. However, conversion to XO only occurs in mammals. The molecular mechanism of this conversion was elucidated in this study. The physiological and pathological significance of this conversion is presented. Finally, enzyme inhibitors were successfully developed, two of which are used as therapeutic agents for gout. Their wide application potential is also discussed. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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15 pages, 2466 KiB

Open AccessReview

The History of Desulfovibrio gigas Aldehyde Oxidoreductase—A Personal View

by José J. G. Moura

Molecules 2023, 28(10), 4229; https://doi.org/10.3390/molecules28104229 - 22 May 2023

Cited by 2 | Viewed by 1370

Abstract

A story going back almost 40 years is presented in this manuscript. This is a different and more challenging way of reporting my research and I hope it will be useful to and target a wide-ranging audience. When preparing the manuscript and collecting [...] Read more.

A story going back almost 40 years is presented in this manuscript. This is a different and more challenging way of reporting my research and I hope it will be useful to and target a wide-ranging audience. When preparing the manuscript and collecting references on the subject of this paper—aldehyde oxidoreductase from Desulfovibrio gigas—I felt like I was travelling back in time (and space), bringing together the people that have contributed most to this area of research. I sincerely hope that I can give my collaborators the credit they deserve. This study is not presented as a chronologic narrative but as a grouping of topics, the development of which occurred over many years. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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18 pages, 3576 KiB

Open AccessReview

The Development of Tungsten Biochemistry—A Personal Recollection

by Wilfred R. Hagen

Molecules 2023, 28(10), 4017; https://doi.org/10.3390/molecules28104017 - 11 May 2023

Cited by 1 | Viewed by 1695

Abstract

The development of tungsten biochemistry is sketched from the viewpoint of personal participation. Following its identification as a bio-element, a catalogue of genes, enzymes, and reactions was built up. EPR spectroscopic monitoring of redox states was, and remains, a prominent tool in attempts [...] Read more.

The development of tungsten biochemistry is sketched from the viewpoint of personal participation. Following its identification as a bio-element, a catalogue of genes, enzymes, and reactions was built up. EPR spectroscopic monitoring of redox states was, and remains, a prominent tool in attempts to understand tungstopterin-based catalysis. A paucity of pre-steady-state data remains a hindrance to overcome to this day. Tungstate transport systems have been characterized and found to be very specific for W over Mo. Additional selectivity is presented by the biosynthetic machinery for tungstopterin enzymes. Metallomics analysis of hyperthermophilic archaeon Pyrococcus furiosus indicates a comprehensive inventory of tungsten proteins. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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18 pages, 2272 KiB

Open AccessReview

Xanthine Oxidase—A Personal History

by Russ Hille

Molecules 2023, 28(4), 1921; https://doi.org/10.3390/molecules28041921 - 17 Feb 2023

Cited by 6 | Viewed by 2211

Abstract

A personal perspective is provided regarding the work in several laboratories, including the author’s, that has established the reaction mechanism of xanthine oxidase and related enzymes. Full article

(This article belongs to the Special Issue Molybdenum and Tungsten Enzymes—State of the Art in Research)

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