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Hydrogenase
A hydrogenase is an enzyme that catalyses the reversible oxidation of molecular hydrogen (H2), as shown below: Hydrogen uptake () is coupled to the reduction of electron acceptors such as oxygen, nitrate, sulfate, carbon dioxide (), and fumarate. On the other hand, proton reduction () is coupled to the oxidation of electron donors such as ferredoxin (FNR), and serves to dispose excess electrons in cells (essential in pyruvate fermentation). Both low-molecular weight compounds and proteins such as FNRs, cytochrome ''c''3, and cytochrome ''c''6 can act as physiological electron donors or acceptors for hydrogenases. Structural classification It has been estimated that 99% of all organisms utilize hydrogen, H2. Most of these species are microbes and their ability to use H2 as a metabolite arises from the expression of metalloenzymes known as hydrogenases. Hydrogenases are sub-classified into three different types based on the active site metal content: iron-iron hydrogenase, ni ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ralstonia Eutropha
''Cupriavidus necator'' is a Gram-negative soil bacterium of the class Betaproteobacteria. Taxonomy ''Cupriavidus necator'' has gone through a series of name changes. In the first half of the 20th century, many micro-organisms were isolated for their ability to use hydrogen. Hydrogen-metabolizing chemolithotrophic organisms were clustered into the group ''Hydrogenomonas''. ''C. necator'' was originally named ''Hydrogenomonas eutrophus'' because it fell under the ''Hydrogenomonas'' classification and was “well nourished and robust”. Some of the original ''H. eutrophus'' cultures isolated were by Bovell and Wilde. After characterizing cell morphology, metabolism and GC content, the ''Hydrogenomonas'' nomenclature was disbanded because it comprised many species of microorganisms. ''H. eutrophus'' was then renamed ''Alcaligenes eutropha'' because it was a micro-organism with degenerated peritrichous flagellation. Investigating phenotype, lipid composition, fatty acid com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Metalloenzyme
Metalloprotein is a generic term for a protein that contains a metal ion cofactor. A large proportion of all proteins are part of this category. For instance, at least 1000 human proteins (out of ~20,000) contain zinc-binding protein domains although there may be up to 3000 human zinc metalloproteins. Abundance It is estimated that approximately half of all proteins contain a metal. In another estimate, about one quarter to one third of all proteins are proposed to require metals to carry out their functions. Thus, metalloproteins have many different functions in cells, such as storage and transport of proteins, enzymes and signal transduction proteins, or infectious diseases. The abundance of metal binding proteins may be inherent to the amino acids that proteins use, as even artificial proteins without evolutionary history will readily bind metals. Most metals in the human body are bound to proteins. For instance, the relatively high concentration of iron in the human body i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Bifurcation
In biochemistry, electron bifurcation (EB) refers to a system that enables an unfavorable (endergonic) transformation by coupling to a favorable (exergonic) transformation. Two electrons are involved: one flows to an acceptor with a "higher reduction potential and the other with a lower reduction potential" than the donor. The process is suspected of being common in bioenergetics. Two versions of EB are recognized. One involves redox of quinones and the other involves flavins. Quinones and flavins are cofactors that are capable of undergoing 2 – 2 proton redox. A pervasive example of electron bifurcation is the Q cycle, which is part of the machinery that results in oxidative phosphorylation. In that case one electron from ubiquinol is directed to a Rieske cluster and the other electron is directed to a cytochrome b Cytochrome b within both molecular and cell biology, is a protein found in the mitochondria of eukaryotic cells. It functions as part of the e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyanide
Cyanide is a naturally occurring, rapidly acting, toxic chemical that can exist in many different forms. In chemistry, a cyanide () is a chemical compound that contains a functional group. This group, known as the cyano group, consists of a carbon atom triple-bonded to a nitrogen atom. In inorganic cyanides, the cyanide group is present as the anion . Soluble salts such as sodium cyanide (NaCN) and potassium cyanide (KCN) are highly toxic. Hydrocyanic acid, also known as hydrogen cyanide, or HCN, is a highly volatile liquid that is produced on a large scale industrially. It is obtained by acidification of cyanide salts. Organic cyanides are usually called nitriles. In nitriles, the group is linked by a covalent bond to carbon. For example, in acetonitrile (), the cyanide group is bonded to methyl (). Although nitriles generally do not release cyanide ions, the cyanohydrins do and are thus rather toxic. Bonding The cyanide ion is isoelectronic with carbon monoxide a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. Almost all metabolic processes in the cell need enzyme catalysis in order to occur at rates fast enough to sustain life. Metabolic pathways depend upon enzymes to catalyze individual steps. The study of enzymes is called ''enzymology'' and the field of pseudoenzyme analysis recognizes that during evolution, some enzymes have lost the ability to carry out biological catalysis, which is often reflected in their amino acid sequences and unusual 'pseudocatalytic' properties. Enzymes are known to catalyze more than 5,000 biochemical reaction types. Other biocatalysts are catalytic RNA molecules, called ribozymes. Enzymes' specificity comes from their unique three-dimensional structures. Like all catalysts, enzymes increase the reaction ra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simplest molecule of the oxocarbon family. In coordination complexes the carbon monoxide ligand is called carbonyl. It is a key ingredient in many processes in industrial chemistry. The most common source of carbon monoxide is the partial combustion of carbon-containing compounds, when insufficient oxygen or heat is present to produce carbon dioxide. There are also numerous environmental and biological sources that generate and emit a significant amount of carbon monoxide. It is important in the production of many compounds, including drugs, fragrances, and fuels. Upon emission into the atmosphere, carbon monoxide affects several processes that contribute to climate change. Carbon monoxide has important biological roles across phylogenetic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Turnover Number
Turnover number has two different meanings: In enzymology, turnover number (also termed ''k''cat) is defined as the maximum number of chemical conversions of substrate molecules per second that a single active site will execute for a given enzyme concentration _T/math> for enzymes with two or more active sites. For enzymes with a single active site, ''k''cat is referred to as the catalytic constant. It can be calculated from the maximum reaction rate V_\max and catalyst site concentration _T/math> as follows: :k_\mathrm = \frac (See Michaelis–Menten kinetics). In other chemical fields, such as organometallic catalysis, turnover number (abbreviated ''TON'') has a different meaning: the number of moles of substrate that a mole of catalyst can convert before becoming inactivated. An ideal catalyst would have an infinite turnover number in this sense, because it would never be consumed. The term turnover frequency (abbreviated ''TOF'') is used to refer to the turnover per unit tim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylogenetics
In biology, phylogenetics (; from Greek language, Greek wikt:φυλή, φυλή/wikt:φῦλον, φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups of organisms. These relationships are determined by Computational phylogenetics, phylogenetic inference methods that focus on observed heritable traits, such as DNA sequences, Protein, protein Amino acid, amino acid sequences, or Morphology (biology), morphology. The result of such an analysis is a phylogenetic tree—a diagram containing a hypothesis of relationships that reflects the evolutionary history of a group of organisms. The tips of a phylogenetic tree can be living taxa or fossils, and represent the "end" or the present time in an evolutionary lineage. A phylogenetic diagram can be rooted or unrooted. A rooted tree diagram indicates the hypothetical common ancestor of the tree. An un ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
International Journal Of Hydrogen Energy
The ''International Journal of Hydrogen Energy'' is a peer-reviewed scientific journal covering all aspects of hydrogen energy, including hydrogen generation and storage. It is published by Elsevier and is an official journal of the International Association for Hydrogen Energy. Established in 1976, the journal became monthly in 1982, biweekly in 2008, 36/yr in 2013, and weekly in 2015. The editor in chief is Turhan Nejat Veziroğlu (University of Miami). Abstracting and indexing The journal is abstracted and indexed in: According to the ''Journal Citation Reports'', the journal has a 2021 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a scientometric index calculated by Clarivate that reflects the yearly mean number of citations of articles published in the last two years in a given journal, as i ... of 7.139. References External links * International Association for Hydrogen Energy Elsevier academic journals Ener ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Electron Transport Chain
An electron transport chain (ETC) is a series of protein complexes and other molecules that transfer electrons from electron donors to electron acceptors via redox reactions (both reduction and oxidation occurring simultaneously) and couples this electron transfer with the transfer of protons (H+ ions) across a membrane. The electrons that transferred from NADH and FADH2 to the ETC involves 4 multi-subunit large enzymes complexes and 2 mobile electron carriers. Many of the enzymes in the electron transport chain are membrane-bound. The flow of electrons through the electron transport chain is an exergonic process. The energy from the redox reactions creates an electrochemical proton gradient that drives the synthesis of adenosine triphosphate (ATP). In aerobic respiration, the flow of electrons terminates with molecular oxygen as the final electron acceptor. In anaerobic respiration, other electron acceptors are used, such as sulfate. In an electron transport chain, the redo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Azadithiolate Cofactor
An azadithiolate cofactor is an anion with the formula NH(CH2S)22−. It is used as a cofactor in the eFehydrogenases, bacterial enzymes responsible for the reversible reduction of 2 H+ to H2. As a cofactor, the two thiolate functional groups are bound to each of the two irons in the active site of the enzyme in a bridging fashion. The amine In chemistry, amines (, ) are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia (), wherein one or more hydrogen atoms have been replaced by a substituen ... functional group serves as an acid/base to transfer H+ from the solution to the active site. The proton transfer function of this cofactor is of great importance to the activity of the hydrogenase enzyme, as H2 evolution will not occur if the amine is not present. References {{Reflist Cofactors ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
