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Dissimilatory Sulfate Reduction
Dissimilatory sulfate reduction is a form of anaerobic respiration that uses sulfate as the terminal electron acceptor to produce hydrogen sulfide. This metabolism is found in some types of bacteria and archaea which are often termed sulfate-reducing organisms. The term "''dissimilatory''" is used when hydrogen sulfide is produced in an anaerobic respiration process. By contrast, the term "''assimilatory''" would be used in relation to the biosynthesis of organosulfur compounds, even though hydrogen sulfide may be an intermediate. Dissimilatory sulfate reduction occurs in four steps: # Conversion (activation) of sulfate to adenosine 5’-phosphosulfate (APS) via sulfate adenylyltransferase # Reduction of APS to sulfite via adenylyl-sulfate reductase # Transfer of the sulfur atom of sulfite to the DsrC protein creating a trisulfide intermediate catalyzed by DsrAB # Reduction of the trisulfide to sulfide and reduced DsrC via a membrane bound enzyme, DsrMKJOP Which requires the cons ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dissimilatory Sulfate Reduction Overall Reactions
In phonology, particularly within historical linguistics, dissimilation is a phenomenon whereby similar consonants or vowels in a word become less similar. In English, dissimilation is particularly common with liquid consonants such as /r/ and /l/ when they occur in a sequence. Examples Dropped initial /r/ in /r..r/ sequence (r-Deletion) When a sound occurs before another in the middle of a word in rhotic dialects of English, the first tends to drop out, as in "" for ''berserk,'' "" for ''surprise,'' "" for ''particular'', and "" for ''governor'' – this does not affect the pronunciation of ''government,'' which has only one , but English ''government'' tends to be pronounced "", dropping out the first n. In English, ''r''-deletion occurs when a syllable is unstressed and may drop out altogether, as in "" for ''deteriorate'' and "" for ''temperature,'' a process called haplology. When the is found in , it may change to . (, ' → ''February,'' which has been explained by p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adenylyl-sulfate Reductase
Adenylyl-sulfate reductase () is an enzyme that catalyzes the chemical reaction of the reduction of adenylyl-sulfate/adenosine-5'-phosphosulfate (APS) to sulfite through the use of an electron donor cofactor. The products of the reaction are AMP and sulfite, as well as an oxidized electron donor cofactor. Nomenclature This enzyme belongs to the family of oxidoreductases, specifically those acting on a sulfur group of donors with other acceptors. The systematic name of this enzyme class is AMP, sulfite:acceptor oxidoreductase (adenosine-5'-phosphosulfate-forming). Other names in common use include adenosine phosphosulfate reductase, adenosine 5'-phosphosulfate reductase, APS-reductase, APS reductase, AMP, sulfite:(acceptor) oxidoreductase, and (adenosine-5'-phosphosulfate-forming). This enzyme participates in selenium metabolism and sulfur metabolism. Mechanism APS reductase catalyzes the reversible transformation of APS to sulfite and AMP, which is the rate determining ste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfur Cycle
The sulfur cycle is a biogeochemical cycle in which the sulfur moves between rocks, waterways and living systems. It is important in geology as it affects many minerals and in life because sulfur is an essential element ( CHNOPS), being a constituent of many proteins and cofactors, and sulfur compounds can be used as oxidants or reductants in microbial respiration. The global sulfur cycle involves the transformations of sulfur species through different oxidation states, which play an important role in both geological and biological processes. Steps of the sulfur cycle are: * Mineralization of organic sulfur into inorganic forms, such as hydrogen sulfide (H2S), elemental sulfur, as well as sulfide minerals. * Oxidation of hydrogen sulfide, sulfide, and elemental sulfur (S) to sulfate (). * Reduction of sulfate to sulfide. * Incorporation of sulfide into organic compounds (including metal-containing derivatives). These are often termed as follows: :''Assimilative sulfate reducti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dissimilatory Sulfite Reductase
Dissimilatory sulfite reductase () is an enzyme that participates in sulfur metabolism in dissimilatory sulfate reduction. The enzyme is essential in prokaryotic sulfur-based energy metabolism, including sulfate/sulfite reducing organisms, sulfur-oxidizing bacteria, and organosulfonate reducers. In sulfur reducers it catalyses the reduction of sulfite to sulfide (reaction 1), while in sulfur oxidizers it catalyses the opposite reaction (reaction 2). The reaction involves the small protein DsrC, which is present in all the organisms that contain dissimilatory sulfite reductase. During the process an intramolecular trisulfide is formed between two L-cysteine residues of DsrC and the sulfur atom from sulfite. This trisulfide can be reduced by a number of proteins including DsrK and TcmB. Reaction in organisms performing dissimilatory sulfate reduction: : (1) sulfite + a srC proteindithiol + 2 reduced acceptor + 2 H+ = hydrogen sulfide + a srC proteindisulfide + 2 acceptor + 3 H2O ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Adenosine Triphosphate
Adenosine triphosphate (ATP) is an organic compound that provides energy to drive many processes in living cells, such as muscle contraction, nerve impulse propagation, condensate dissolution, and chemical synthesis. Found in all known forms of life, ATP is often referred to as the "molecular unit of currency" of intracellular energy transfer. When consumed in metabolic processes, it converts either to adenosine diphosphate (ADP) or to adenosine monophosphate (AMP). Other processes regenerate ATP. The human body recycles its own body weight equivalent in ATP each day. It is also a precursor to DNA and RNA, and is used as a coenzyme. From the perspective of biochemistry, ATP is classified as a nucleoside triphosphate, which indicates that it consists of three components: a nitrogenous base (adenine), the sugar ribose, and the Polyphosphate, triphosphate. Structure ATP consists of an adenine attached by the 9-nitrogen atom to the 1′ carbon atom of a sugar (ribose), which i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
ATP Sulfurylase
In enzymology, a sulfate adenylyltransferase () is an enzyme that catalyzes the chemical reaction :ATP + sulfate \rightleftharpoonspyrophosphate + adenylyl sulfate Thus, the two substrates of this enzyme are ATP and sulfate, whereas its two products are pyrophosphate and adenylyl sulfate. This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing nucleotide groups (nucleotidyltransferases). The systematic name of this enzyme class is ATP:sulfate adenylyltransferase. Other names in common use include adenosine-5'-triphosphate sulfurylase, adenosinetriphosphate sulfurylase, adenylylsulfate pyrophosphorylase, ATP sulfurylase, ATP-sulfurylase, and sulfurylase. This enzyme participates in 3 metabolic pathways: purine metabolism, selenoamino acid metabolism, and sulfur metabolism. Some sulfate adenylyltransferases are part of a bifunctional polypeptide chain associated with adenosyl phosphosulfate (APS) kinase. Both enzymes are r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ferrodoxin
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 acc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
NADH
Nicotinamide adenine dinucleotide (NAD) is a coenzyme central to metabolism. Found in all living cells, NAD is called a dinucleotide because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine nucleobase and the other nicotinamide. NAD exists in two forms: an oxidized and reduced form, abbreviated as NAD and NADH (H for hydrogen), respectively. In metabolism, nicotinamide adenine dinucleotide is involved in redox reactions, carrying electrons from one reaction to another. The cofactor is, therefore, found in two forms in cells: NAD is an oxidizing agent – it accepts electrons from other molecules and becomes reduced. This reaction, also with H+, forms NADH, which can then be used as a reducing agent to donate electrons. These electron transfer reactions are the main function of NAD. However, it is also used in other cellular processes, most notably as a substrate of enzymes in adding or removing chemical groups t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfide
Sulfide (British English also sulphide) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to chemical compounds large families of inorganic and organic compounds, e.g. lead sulfide and dimethyl sulfide. Hydrogen sulfide (H2S) and bisulfide (SH−) are the conjugate acids of sulfide. Chemical properties The sulfide ion, S2−, does not exist in aqueous alkaline solutions of Na2S. Instead sulfide converts to hydrosulfide: :S2− + H2O → SH− + OH− Upon treatment with an acid, sulfide salts convert to hydrogen sulfide: :S2− + H+ → SH− :SH− + H+ → H2S Oxidation of sulfide is a complicated process. Depending on the conditions, the oxidation can produce elemental sulfur, polysulfides, polythionates, sulfite, or sulfate. Metal sulfides react with halogens, forming sulfur and metal salts. :8 MgS + 8 I2 → S8 + 8 M ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfite
Sulfites or sulphites are compounds that contain the sulfite ion (or the sulfate(IV) ion, from its correct systematic name), . The sulfite ion is the conjugate base of bisulfite. Although its acid ( sulfurous acid) is elusive, its salts are widely used. Sulfites are substances that naturally occur in some foods and the human body. They are also used as regulated food additives. When in food or drink, sulfites are often lumped together with sulfur dioxide.SeREGULATION (EU) No 1169/2011 OF THE EUROPEAN PARLIAMENT AND OF THE COUNCIL/ref> Structure The structure of the sulfite anion can be described with three equivalent resonance structures. In each resonance structure, the sulfur atom is double-bonded to one oxygen atom with a formal charge of zero (neutral), and sulfur is singly bonded to the other two oxygen atoms, which each carry a formal charge of −1, together accounting for the −2 charge on the anion. There is also a non-bonded lone pair on the sulfur, so the structu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Anaerobic Respiration
Anaerobic respiration is respiration using electron acceptors other than molecular oxygen (O2). Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain. In aerobic organisms undergoing respiration, electrons are shuttled to an electron transport chain, and the final electron acceptor is oxygen. Molecular oxygen is an excellent electron acceptor. Anaerobes instead use less-oxidizing substances such as nitrate (), fumarate (), sulfate (), or elemental sulfur (S). These terminal electron acceptors have smaller reduction potentials than O2. Less energy per oxidized molecule is released. Therefore, anaerobic respiration is less efficient than aerobic. As compared with fermentation Anaerobic cellular respiration and fermentation generate ATP in very different ways, and the terms should not be treated as synonyms. Cellular respiration (both aerobic and anaerobic) uses highly reduced chemical compounds such as NADH and FADH2 ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sulfate Adenylyltransferase
In enzymology, a sulfate adenylyltransferase () is an enzyme that catalyzes the chemical reaction :ATP + sulfate \rightleftharpoonspyrophosphate + adenylyl sulfate Thus, the two substrates of this enzyme are ATP and sulfate, whereas its two products are pyrophosphate and adenylyl sulfate. This enzyme belongs to the family of transferases, specifically those transferring phosphorus-containing nucleotide groups (nucleotidyltransferases). The systematic name of this enzyme class is ATP:sulfate adenylyltransferase. Other names in common use include adenosine-5'-triphosphate sulfurylase, adenosinetriphosphate sulfurylase, adenylylsulfate pyrophosphorylase, ATP sulfurylase, ATP-sulfurylase, and sulfurylase. This enzyme participates in 3 metabolic pathways: purine metabolism, selenoamino acid metabolism, and sulfur metabolism. Some sulfate adenylyltransferases are part of a bifunctional polypeptide chain associated with adenosyl phosphosulfate (APS) kinase. Both enzymes are r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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