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Ferredoxin
Ferredoxins (from Latin ''ferrum'': iron + redox, often abbreviated "fd") are iron–sulfur proteins that mediate electron transfer in a range of metabolic reactions. The term "ferredoxin" was coined by D.C. Wharton of the DuPont Co. and applied to the "iron protein" first purified in 1962 by Mortenson, Valentine, and Carnahan from the anaerobic bacterium '' Clostridium pasteurianum''. Another redox protein, isolated from spinach chloroplasts, was termed "chloroplast ferredoxin". The chloroplast ferredoxin is involved in both cyclic and non-cyclic photophosphorylation reactions of photosynthesis. In non-cyclic photophosphorylation, ferredoxin is the last electron acceptor thus reducing the enzyme NADP+ reductase. It accepts electrons produced from sunlight- excited chlorophyll and transfers them to the enzyme ferredoxin: NADP+ oxidoreductase . Ferredoxins are small proteins containing iron and sulfur atoms organized as iron–sulfur clusters. These biological " capacitors" can ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pyruvate Synthase
In enzymology, a pyruvate synthase () is an enzyme that catalyzes the interconversion of pyruvate and acetyl-CoA. It is also called pyruvate:ferredoxin oxidoreductase (PFOR). The relevant equilibrium catalysed by PFOR is: :pyruvate + CoA + oxidized ferredoxin \rightleftharpoons acetyl-CoA + CO2 + reduced ferredoxin The 3 substrates of this enzyme are pyruvate, CoA, and oxidized ferredoxin, whereas its 3 products are acetyl-CoA, CO2, and reduced ferredoxin. Function This enzyme participates in 4 metabolic pathways: pyruvate metabolism, propanoate metabolism, butanoate metabolism, and reductive carboxylate cycle ( fixation). Its major role is the extraction of reducing equivalents by the decarboxylation. In aerobic organisms, this conversion is catalysed by pyruvate dehydrogenase, also uses thiamine pyrophosphate (TPP) but relies on lipoate as the electron acceptor. Unlike the aerobic enzyme complex PFOR transfers reducing equivalents to flavins or iron-sulflur clusters. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glyceraldehyde-3-phosphate Dehydrogenase (ferredoxin)
In enzymology, a glyceraldehyde-3-phosphate dehydrogenase (ferredoxin) () is an enzyme that catalyzes the chemical reaction :D-glyceraldehyde-3-phosphate + H2O + 2 oxidized ferredoxin \rightleftharpoons 3-phospho-D-glycerate + 2 H+ + 2 reduced ferredoxin The 3 substrates of this enzyme are D-glyceraldehyde-3-phosphate, H2O, and oxidized ferredoxin, whereas its 3 products are 3-phospho-D-glycerate, H+, and reduced ferredoxin. This enzyme belongs to the family of oxidoreductases, specifically those acting on the aldehyde or oxo group of donor with an iron-sulfur protein as acceptor. The systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature. A semisystematic name or semitrivial ... of this enzyme class is D-glyceraldehyde-3-phosphate:ferredoxin oxidoreductase. Other names in common use include GAPOR, glycer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron–sulfur Protein
Iron–sulfur proteins (or iron–sulphur proteins in British spelling) are proteins characterized by the presence of iron–sulfur clusters containing sulfide-linked di-, tri-, and tetrairon centers in variable oxidation states. Iron–sulfur clusters are found in a variety of metalloproteins, such as the ferredoxins, as well as NADH dehydrogenase, hydrogenases, coenzyme Q – cytochrome c reductase, succinate – coenzyme Q reductase and nitrogenase. Iron–sulfur clusters are best known for their role in the oxidation-reduction reactions of electron transport in mitochondria and chloroplasts. Both Complex I and Complex II of oxidative phosphorylation have multiple Fe–S clusters. They have many other functions including catalysis as illustrated by aconitase, generation of radicals as illustrated by SAM-dependent enzymes, and as sulfur donors in the biosynthesis of lipoic acid and biotin. Additionally, some Fe–S proteins regulate gene expression. Fe–S proteins are vulner ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rieske Protein
Rieske proteins are iron–sulfur protein (ISP) components of cytochrome ''bc''1 complexes and cytochrome b6f complexes and are responsible for electron transfer in some biological systems. John S. Rieske and co-workers first discovered the protein and in 1964 isolated an acetylated form of the bovine mitochondrial protein. In 1979 Trumpower's lab isolated the "oxidation factor" from bovine mitochondria and showed it was a reconstitutively-active form of the Rieske iron-sulfur protein It is a unique Fe-2Scluster in that one of the two Fe atoms is coordinated by two histidine residues rather than two cysteine residues. They have since been found in plants, animals, and bacteria with widely ranging electron reduction potentials from -150 to +400 mV. Biological function Ubiquinol-cytochrome-c reductase (also known as bc1 complex or complex III) is an enzyme complex of bacterial and mitochondrial oxidative phosphorylation systems. It catalyses the oxidation-reduction reaction ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photophosphorylation
In the process of photosynthesis, the phosphorylation of ADP to form ATP using the energy of sunlight is called photophosphorylation. Cyclic photophosphorylation occurs in both aerobic and anaerobic conditions, driven by the main primary source of energy available to living organisms, which is sunlight. All organisms produce a phosphate compound, ATP, which is the universal energy currency of life. In photophosphorylation, light energy is used to pump protons across a biological membrane, mediated by flow of electrons through an electron transport chain. This stores energy in a proton gradient. As the protons flow back through an enzyme called ATP synthase, ATP is generated from ADP and inorganic phosphate. ATP is essential in the Calvin cycle to assist in the synthesis of carbohydrates from carbon dioxide and NADPH. ATP and reactions Both the structure of ATP synthase and its underlying gene are remarkably similar in all known forms of life. ATP synthase is powered by a transmembr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Table Of Standard Reduction Potentials For Half-reactions Important In Biochemistry
The values below are standard apparent reduction potentials for electro-biochemical half-reactions measured at 25 °C, 1 atmosphere and a pH of 7 in aqueous solution. The actual physiological potential depends on the ratio of the reduced () and oxidized () forms according to the Nernst equation and the thermal voltage. When an oxidizer () accepts a number ''z'' of electrons () to be converted in its reduced form (), the half-reaction is expressed as: : + ''z'' → The reaction quotient (r) is the ratio of the chemical activity (''a''i) of the reduced form (the reductant, ''a''Red) to the activity of the oxidized form (the oxidant, ''a''ox). It is equal to the ratio of their concentrations (''C''i) only if the system is sufficiently diluted and the activity coefficients (''γ''i) are close to unity (''a''i = ''γ''i ''C''i): : Q_r = \frac = \frac The Nernst equation is a function of and can be written as follows: E_\text = E^\ominus_\text - \frac \ln Q_r=E^\ominus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron–sulfur Cluster
Iron–sulfur clusters (or iron–sulphur clusters in British spelling) are molecular ensembles of iron and sulfide. They are most often discussed in the context of the biological role for iron–sulfur proteins, which are pervasive. Many Fe–S clusters are known in the area of organometallic chemistry and as precursors to synthetic analogues of the biological clusters (see Figure). It is believed that the last universal common ancestor had many iron-sulfur clusters. Organometallic clusters Organometallic Fe–S clusters include the sulfido carbonyls with the formula Fe2S2(CO)6, H2Fe3S(CO)9, and Fe3S2(CO)9. Compounds are also known that incorporate cyclopentadienyl ligands, such as (C5H5)4Fe4S4. Inorganic materials center, Structure of potassium dithioferrate, which features infinite chains of Fe(III) centers. Biological Fe–S clusters Iron–sulfur clusters occur in many biological systems, often as components of electron transfer proteins. The ferredoxin proteins a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Monoxide Dehydrogenase
In enzymology, carbon monoxide dehydrogenase (CODH) () is an enzyme that catalyzes the chemical reaction :CO + H2O + A \rightleftharpoons CO2 + AH2 The chemical process catalyzed by carbon monoxide dehydrogenase is similar to the water-gas shift reaction. The 3 substrates of this enzyme are CO, H2O, and A, whereas its two products are CO2 and AH2. A variety of electron donors/receivers (Shown as "A" and "AH2" in the reaction equation above) are observed in micro-organisms which utilize CODH. Several examples of electron transfer cofactors has been proposed, including Ferredoxin, NADP+/NADPH and flavoprotein complexes like flavin adenine dinucleotide (FAD) as well as hydrogenases. CODHs support the metabolisms of diverse prokaryotes, including methanogens, aerobic carboxidotrophs, acetogens, sulfate-reducers, and hydrogenogenic bacteria. The bidirectional reaction catalyzed by CODH plays a role in the carbon cycle allowing organisms to both make use of CO as a source of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chloroplast
A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in the energy-storage molecules ATP and NADPH while freeing oxygen from water in the cells. The ATP and NADPH is then used to make organic molecules from carbon dioxide in a process known as the Calvin cycle. Chloroplasts carry out a number of other functions, including fatty acid synthesis, amino acid synthesis, and the immune response in plants. The number of chloroplasts per cell varies from one, in unicellular algae, up to 100 in plants like ''Arabidopsis'' and wheat. A chloroplast is characterized by its two membranes and a high concentration of chlorophyll. Other plastid types, such as the leucoplast and the chromoplast, contain little chlorophyll and do not carry out photosynthesis. Chloroplasts are highly dynamic—they circulat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bioinorganic
Bioinorganic chemistry is a field that examines the role of metals in biology. Bioinorganic chemistry includes the study of both natural phenomena such as the behavior of metalloproteins as well as artificially introduced metals, including those that are non-essential, in medicine and toxicology. Many biological processes such as respiration depend upon molecules that fall within the realm of inorganic chemistry. The discipline also includes the study of inorganic models or mimics that imitate the behaviour of metalloproteins. As a mix of biochemistry and inorganic chemistry, bioinorganic chemistry is important in elucidating the implications of electron-transfer proteins, substrate bindings and activation, atom and group transfer chemistry as well as metal properties in biological chemistry. The successful development of truly interdisciplinary work is necessary to advance bioinorganic chemistry. Composition of living organisms About 99% of mammals' mass are the elements carb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in front of oxygen (32.1% and 30.1%, respectively), forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust. In its metallic state, iron is rare in the Earth's crust, limited mainly to deposition by meteorites. Iron ores, by contrast, are among the most abundant in the Earth's crust, although extracting usable metal from them requires kilns or furnaces capable of reaching or higher, about higher than that required to smelt copper. Humans started to master that process in Eurasia during the 2nd millennium BCE and the use of iron tools and weapons began to displace copper alloys, in some regions, only around 1200 BCE. That event is considered the transition from the Bronze Age to the Iron A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rubredoxin
Rubredoxins are a class of low-molecular-weight iron-containing proteins found in sulfur-metabolizing bacteria and archaea. Sometimes rubredoxins are classified as iron-sulfur proteins; however, in contrast to iron-sulfur proteins, rubredoxins do not contain inorganic sulfide. Like cytochromes, ferredoxins and Rieske proteins, rubredoxins participate in electron transfer in biological systems. Structure The 3-D structures of a number of rubredoxins have been solved. The fold belongs to the α+β class, with 2 α-helices and 2-3 β-strands. Rubredoxin active site contains an iron ion which is coordinated by the sulfurs of four conserved cysteine residues forming an almost regular tetrahedron. This is sometimes denoted as a Fe-0Sor an Fe1S0 system, in analogy to the nomenclature for iron-sulfur proteins. While the vast majority of rubredoxins are soluble, there exists a membrane-bound rubredoxin, referred to as rubredoxin A, in oxygenic photoautotrophs. Rubredoxins perform on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
