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Information about Coenzyme

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Coenzyme A
Coenzymes are small organic non-protein molecules that carry chemical groups between enzymes. They are substrates for enzymes and do not usually form a permanent part of the enzymes' structures. This distinguishes coenzymes from cofactors, which are non-protein components that are bound to enzymes - such as iron-sulfur centers, flavin or haem groups.

In metabolism, coenzymes are involved in both group-transfer reactions, for example coenzyme A and adenosine triphosphate, and redox reactions, for example coenzyme Q10 and nicotinamide adenine dinucleotide. These molecules are often vitamins or are made from vitamins.

Terminology

The term coenzymes is commonly used loosely, and coenzymes can also be defined as organic, non-protein cofactors.[1] Coenzymes are also sometimes referred to as cosubstrates, but this usage is unusual.

Coenzymes are consumed in the reactions in which they are substrates, for example: the coenzyme NADH is converted to NAD+ by oxidoreductases. Coenzymes are however regenerated and their concentration maintained at a steady level in the cell.

A special subset of coenzymes are prosthetic groups. These have more in common with cofactors since they are tightly bound to enzymes and are not released as part of the reaction. Prosthetic groups include molybdopterin, lipoamide and biotin.

Coenzymes as metabolic intermediates

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Space-filling model of the coenzyme nicotinamide adenine dinucleotide.
Metabolism involves a vast array of chemical reactions, but most fall under a few basic types of reactions that involve the transfer of functional groups.[2] This common chemistry allows cells to use a small set of metabolic intermediates to carry chemical groups between different reactions.[3] These group-transfer intermediates are the coenzymes.

Each class of group-transfer reaction is carried out by a particular coenzyme, which is the substrate for a set of enzymes that produce it, and a set of enzymes that consume it. An example of this are the dehydrogenases that use nicotinamide adenine dinucleotide (NADH) as a cofactor. Here, hundreds of separate types of enzymes remove electrons from their substrates and reduce NADH and this reduced coenzyme is then a substrate for any of the reductases in the cell that need to reduce their substrates.[4]

Types

Many coenzymes are phosphorylated water-soluble vitamins. Coenzymes are also commonly made from nucleotides such as adenosine triphosphate, the biochemical carrier of phosphate groups, or coenzyme A, the coenzyme that carries acyl groups.

Vitamin and nucleotide derivatives

Not related to vitamins

  • Coenzyme Q. (Coenzyme Q is unusual as it carries electrons between enzymes by diffusing within cell membranes, as this coenzyme is not water soluble. )
  • Molybdopterin

Evolution

Further information: Abiogenesis
Coenzymes such as ATP and NAD(P)H form a core of metabolism that are present in all known forms of life. Such universal conservation indicates that these molecules evolved very early in the development of living things.[5] The current set of coenzymes were therefore probably present in the last universal ancestor, which lived about 4 billion years ago.[6][7]

Coenzymes may even have been present earlier in the history of life on Earth. Interestingly, the nucleotide adenosine is present in coenzymes that catalyse many basic metabolic reactions such as methyl, acyl, and phosphoryl group transfer and redox reactions. This ubiquitous chemical scaffold has been hypothesised to be a remnant of the RNA world, with early ribozymes evolving to bind a restricted set of nucleotides and related compounds.[8][9] Adenosine-based coenzymes are thought to have acted as interchangeable adaptors that allowed enzymes and ribozymes to bind new coenzymes through small modifications in existing adenosine-binding domains, which had evolved to bind a different cofactor.[10]

See also

References

1. ^ Nelson, David L.; Michael M. Cox (2005). Lehninger Principles of Biochemistry. New York: W. H. Freeman and company, 841. ISBN 0-7167-4339-6. 
2. ^ Mitchell P (1979). "The Ninth Sir Hans Krebs Lecture. Compartmentation and communication in living systems. Ligand conduction: a general catalytic principle in chemical, osmotic and chemiosmotic reaction systems". Eur J Biochem 95 (1): 1-20. PMID 378655. 
3. ^ Wimmer M, Rose I. "Mechanisms of enzyme-catalyzed group transfer reactions". Annu Rev Biochem 47: 1031-78. PMID 354490. 
4. ^ Pollak N, Dölle C, Ziegler M (2007). "The power to reduce: pyridine nucleotides--small molecules with a multitude of functions". Biochem J 402 (2): 205-18. PMID 17295611. 
5. ^ Chen X, Li N, Ellington AD (2007). "Ribozyme catalysis of metabolism in the RNA world". Chem. Biodivers. 4 (4): 633–55. PMID 17443876. 
6. ^ Koch A (1998). "How did bacteria come to be?". Adv Microb Physiol 40: 353-99. PMID 9889982. 
7. ^ Ouzounis C, Kyrpides N (1996). "The emergence of major cellular processes in evolution". FEBS Lett 390 (2): 119-23. PMID 8706840. 
8. ^ Saran D, Frank J, Burke DH (2003). "The tyranny of adenosine recognition among RNA aptamers to coenzyme A". BMC Evol. Biol. 3: 26. PMID 14687414. 
9. ^ Jadhav VR, Yarus M (2002). "Coenzymes as coribozymes". Biochimie 84 (9): 877–88. PMID 12458080. 
10. ^ Denessiouk KA, Rantanen VV, Johnson MS (2001). "Adenine recognition: a motif present in ATP-, CoA-, NAD-, NADP-, and FAD-dependent proteins". Proteins 44 (3): 282–91. PMID 11455601. 

External links

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Proteins: enzymes
TopicsActive site - Allosteric regulation - Binding site - Catalytically perfect enzyme - Coenzyme - Cofactor - Cooperativity - EC number
Enzyme catalysis - Enzyme inhibitor - Enzyme kinetics - Lineweaver-Burk plot - Michaelis-Menten kinetics - List of enzymes
TypesEC1 Oxidoreductases/list - EC2 Transferases/list - EC3 Hydrolases/list - EC4 Lyases/list - EC5 Isomerases/list - EC6 Ligases/list
organic compounds]] An organic compound is any member of a large class of chemical compounds whose molecules contain carbon; for historical reasons discussed below, a few types of compounds such as carbonates, carbon oxides and cyanides, as well as elemental carbon are
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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molecule is defined as a sufficiently stable electrically neutral group of at least two atoms in a definite arrangement held together by strong chemical bonds.[1][2] In organic chemistry and biochemistry, the term molecule
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Enzymes are proteins that catalyze (i.e. accelerate) chemical reactions.[1] In enzymatic reactions, the molecules at the beginning of the process are called substrates, and the enzyme converts them into different molecules, the products.
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Cofactor may refer to any of the following:
  • Cofactor (linear algebra) The signed minor of a matrix
  • Minor (linear algebra) as an alternative name for the determinant of a smaller matrix than that which it describes

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Iron-sulfur proteins are proteins characterized by the presence of polymetallic systems (iron-sulfur clusters) containing sulfide ions, in which the iron ions have variable oxidation states.
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Flavin is a tricyclic heteronuclear organic ring based on pteridine whose biochemical source is the vitamin riboflavin. The flavin moiety is often attached with an adenosine diphosphate to form flavin adenine dinucleotide (FAD
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A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. Not all porphyrins contain iron, but a substantial fraction of porphyrin-containing metalloproteins have heme as
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Metabolism is the complete set of chemical reactions that occur in living cells. These processes are the basis of life, allowing cells to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories.
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Coenzyme A (CoA, CoASH, or HSCoA) is a coenzyme, notable for its role in the synthesis and oxidization of fatty acids, and the oxidation of pyruvate in the citric acid cycle. It is adapted from cysteamine, pantothenate, and adenosine triphosphate.
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Adenosine 5'-triphosphate (ATP) is a multifunctional nucleotide that is most important as a "molecular currency" of intracellular energy transfer. In this role, ATP transports chemical energy within cells for metabolism.
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Coenzyme Q10 (also known as ubiquinone, ubidecarenone, coenzyme Q, and abbreviated at times to CoQ10, CoQ, Q10, or Q) is a benzoquinone, where Q refers to the quinone chemical group, and 10 refers to the isoprenyl chemical subunits.
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Nicotinamide adenine dinucleotide (NAD+ or in older notation DPN+) is an important coenzyme found in cells. It plays key roles as a carrier of electrons and a participant in metabolic redox reactions, as well as in cell signaling.
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A vitamin is a nutrient that is an organic compound required in tiny amounts for essential metabolic reactions in a living organism.[1] The term vitamin
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Proteins are large organic compounds made of amino acids arranged in a linear chain and joined together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
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EC1 Oxidoreductases/list - EC2 Transferases/list - EC3 Hydrolases/list - EC4 Lyases/list - EC5 Isomerases/list - EC6 Ligases/list
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In biochemistry, an oxidoreductase is an enzyme that catalyzes the transfer of electrons from one molecule (the reductant, also called the hydrogen acceptor or electron donor) to another (the oxidant, also called the hydrogen donor or electron acceptor).
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A prosthetic group is a non-protein (non-amino acid) component of a conjugated protein. The prosthetic group may be organic (such as a vitamin, sugar, or lipid) or inorganic (such as a metal ion). Prosthetic groups usually bond covalently to their protein.
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EC1 Oxidoreductases/list - EC2 Transferases/list - EC3 Hydrolases/list - EC4 Lyases/list - EC5 Isomerases/list - EC6 Ligases/list
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Molybdopterins are a class of biochemical cofactors that are used in many different enzymes. The simplest structure of molybdopterin contains a pyranopterin coordinated to molybdenum. The pyranopterin structure is a fused ring system containing a pyran fused to pterin.
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Lipoamide is a trivial name for 6,8-dithiooctanoic amide. It is 6,8-dithiooctanoic acid's functional form where the carboxyl group is attached to protein (or any other amine) by an amide linkage (containing -NH2) to an amino group.
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Biotin, also known as vitamin H or B 7 , has the chemical formula C10H16N2O3S (Biotin; Coenzyme R, Biopeiderm), is a water-soluble B-complex vitamin which is composed of an ureido (tetrahydroimidizalone) ring fused with a
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In organic chemistry, functional groups (or moieties) are specific groups of atoms within molecules, that are responsible for the characteristic chemical reactions of those molecules.
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A dehydrogenase is an enzyme that oxidizes a substrate by transferring one or more protons and a pair of electrons to an acceptor, usually NAD/NADP or a flavin coenzyme such as FAD or FMN.
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Nicotinamide adenine dinucleotide (NAD+ or in older notation DPN+) is an important coenzyme found in cells. It plays key roles as a carrier of electrons and a participant in metabolic redox reactions, as well as in cell signaling.
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Redox (shorthand for reduction/oxidation reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed.

This can be either a simple redox process such as the oxidation of carbon to yield carbon dioxide, or the
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A reductase is an enzyme which lowers the activation energy for a reduction reaction. [1][2]

Examples

  • 5-alpha reductase
  • Dihydrofolate reductase
  • HMG-CoA reductase
  • Methemoglobin reductase
  • Ribonucleotide reductase

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Phosphorylation is the addition of a phosphate (PO4) group to a protein molecule or a small molecule. Another way to define it would be the introduction of a phosphate group into an organic molecule.
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Water is a common chemical substance that is essential to all known forms of life.[1] In typical usage, water refers only to its liquid form or state, but the substance also has a solid state, ice, and a gaseous state, water vapor.
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A vitamin is a nutrient that is an organic compound required in tiny amounts for essential metabolic reactions in a living organism.[1] The term vitamin
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