Prosthetic group

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A prosthetic group is the non-amino acid component that is part of the structure of the heteroproteins or conjugated proteins, being tightly linked to the apoprotein.

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Not to be confused with the cosubstrate that binds to the enzyme apoenzyme (either a holoprotein or heteroprotein) by non-covalent binding a non-protein (non-amino acid)

This is a component of a conjugated protein that is required for the protein's biological activity. [1] The prosthetic group may be organic (such as a vitamin, sugar, RNA, phosphate or lipid) or inorganic (such as a metal ion). Prosthetic groups are bound tightly to proteins and may even be attached through a covalent bond. They often play an important role in enzyme catalysis. A protein without its prosthetic group is called an apoprotein, while a protein combined with its prosthetic group is called a holoprotein. A non-covalently bound prosthetic group cannot generally be removed from the holoprotein without denaturating the protein. Thus, the term "prosthetic group" is a very general one and its main emphasis is on the tight character of its binding to the apoprotein. It defines a structural property, in contrast to the term "coenzyme" that defines a functional property.

Prosthetic groups are a subset of cofactors. Loosely bound metal ions and coenzymes are still cofactors, but are generally not called prosthetic groups. [2] [3] [4] In enzymes, prosthetic groups are involved in the catalytic mechanism and required for activity. Other prosthetic groups have structural properties. This is the case for the sugar and lipid moieties in glycoproteins and lipoproteins or RNA in ribosomes. They can be very large, representing the major part of the protein in proteoglycans for instance.

The heme group in hemoglobin is a prosthetic group. Further examples of organic prosthetic groups are vitamin derivatives: thiamine pyrophosphate, pyridoxal-phosphate and biotin. Since prosthetic groups are often vitamins or made from vitamins, this is one of the reasons why vitamins are required in the human diet. Inorganic prosthetic groups are usually transition metal ions such as iron (in heme groups, for example in cytochrome c oxidase and hemoglobin), zinc (for example in carbonic anhydrase), copper (for example in complex IV of the respiratory chain) and molybdenum (for example in nitrate reductase).

List of prosthetic groups

The table below contains a list of some of the most common prosthetic groups.

Prosthetic groupFunctionDistribution
Flavin mononucleotide   [5] Redox reactions Bacteria, archaea and eukaryotes
Flavin adenine dinucleotide   [5] Redox reactions Bacteria, archaea and eukaryotes
Pyrroloquinoline quinone   [6] Redox reactions Bacteria
Pyridoxal phosphate   [7] Transamination, decarboxylation and deamination Bacteria, archaea and eukaryotes
Biotin   [8] Carboxylation Bacteria, archaea and eukaryotes
Methylcobalamin   [9] Methylation and isomerisation Bacteria, archaea and eukaryotes
Thiamine pyrophosphate   [10] Transfer of 2-carbon groups, α cleavage Bacteria, archaea and eukaryotes
Heme   [11] Oxygen binding and redox reactions Bacteria, archaea and eukaryotes
Molybdopterin   [12] [13] Oxygenation reactions Bacteria, archaea and eukaryotes
Lipoic acid   [14] Redox reactions Bacteria, archaea and eukaryotes
Cofactor F430 Methanogenesis Archaea

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<span class="mw-page-title-main">Thiamine</span> Chemical compound

Thiamine, also known as thiamin and vitamin B1, is a vitamin, an essential micronutrient for humans and animals. It is found in food and commercially synthesized to be a dietary supplement or medication. Phosphorylated forms of thiamine are required for some metabolic reactions, including the breakdown of glucose and amino acids.

<span class="mw-page-title-main">Hemoprotein</span> Protein containing a heme prosthetic group

A hemeprotein, or heme protein, is a protein that contains a heme prosthetic group. They are a very large class of metalloproteins. The heme group confers functionality, which can include oxygen carrying, oxygen reduction, electron transfer, and other processes. Heme is bound to the protein either covalently or noncovalently or both.

<span class="mw-page-title-main">Heme</span> Chemical coordination complex of an iron ion chelated to a porphyrin

Heme, or haem, is a precursor to hemoglobin, which is necessary to bind oxygen in the bloodstream. Heme is biosynthesized in both the bone marrow and the liver.

<span class="mw-page-title-main">Biomolecule</span> Molecule that is produced by a living organism

A biomolecule or biological molecule is a loosely used term for molecules present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development. Biomolecules include large macromolecules such as proteins, carbohydrates, lipids, and nucleic acids, as well as small molecules such as primary metabolites, secondary metabolites and natural products. A more general name for this class of material is biological materials. Biomolecules are an important element of living organisms, those biomolecules are often endogenous, produced within the organism but organisms usually need exogenous biomolecules, for example certain nutrients, to survive.

<span class="mw-page-title-main">Cofactor (biochemistry)</span> Non-protein chemical compound or metallic ion

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<span class="mw-page-title-main">Pyrroloquinoline quinone</span> Chemical compound

Pyrroloquinoline quinone (PQQ), also called methoxatin, is a redox cofactor and antioxidant. Produced by bacteria, it is found in soil and foods such as kiwifruit, as well as human breast milk. Enzymes using PQQ as a redox cofactor are called quinoproteins and play a variety of redox roles. Quinoprotein glucose dehydrogenase is used as a glucose sensor in bacteria. PQQ stimulates growth in bacteria. Eukaryote targets, including mammalian lactate dehydrogenase, are of more interest to health. It is suggested that PQQ taken as a dietary supplement could promote mitochondrial biogenesis via this pathway as well as PGC-1α.

<span class="mw-page-title-main">Aminolevulinic acid synthase</span> Class of enzymes

Aminolevulinic acid synthase (ALA synthase, ALAS, or delta-aminolevulinic acid synthase) is an enzyme (EC 2.3.1.37) that catalyzes the synthesis of δ-aminolevulinic acid (ALA) the first common precursor in the biosynthesis of all tetrapyrroles such as hemes, cobalamins and chlorophylls. The reaction is as follows:

<span class="mw-page-title-main">Pyridoxal phosphate</span> Active form of vitamin B6

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<span class="mw-page-title-main">Succinate dehydrogenase</span> Enzyme

Succinate dehydrogenase (SDH) or succinate-coenzyme Q reductase (SQR) or respiratory complex II is an enzyme complex, found in many bacterial cells and in the inner mitochondrial membrane of eukaryotes. It is the only enzyme that participates in both the citric acid cycle and the electron transport chain. Histochemical analysis showing high succinate dehydrogenase in muscle demonstrates high mitochondrial content and high oxidative potential.

<span class="mw-page-title-main">Flavin adenine dinucleotide</span> Redox-active coenzyme

In biochemistry, flavin adenine dinucleotide (FAD) is a redox-active coenzyme associated with various proteins, which is involved with several enzymatic reactions in metabolism. A flavoprotein is a protein that contains a flavin group, which may be in the form of FAD or flavin mononucleotide (FMN). Many flavoproteins are known: components of the succinate dehydrogenase complex, α-ketoglutarate dehydrogenase, and a component of the pyruvate dehydrogenase complex.

<span class="mw-page-title-main">Transketolase</span> Enzyme involved in metabolic pathways

Transketolase is an enzyme that, in humans, is encoded by the TKT gene. It participates in both the pentose phosphate pathway in all organisms and the Calvin cycle of photosynthesis. Transketolase catalyzes two important reactions, which operate in opposite directions in these two pathways. In the first reaction of the non-oxidative pentose phosphate pathway, the cofactor thiamine diphosphate accepts a 2-carbon fragment from a 5-carbon ketose (D-xylulose-5-P), then transfers this fragment to a 5-carbon aldose (D-ribose-5-P) to form a 7-carbon ketose (sedoheptulose-7-P). The abstraction of two carbons from D-xylulose-5-P yields the 3-carbon aldose glyceraldehyde-3-P. In the Calvin cycle, transketolase catalyzes the reverse reaction, the conversion of sedoheptulose-7-P and glyceraldehyde-3-P to pentoses, the aldose D-ribose-5-P and the ketose D-xylulose-5-P.

A holoprotein or conjugated protein is an apoprotein combined with its prosthetic group.

<span class="mw-page-title-main">Enzyme catalysis</span> Catalysis of chemical reactions by specialized proteins known as enzymes

Enzyme catalysis is the increase in the rate of a process by a biological molecule, an "enzyme". Most enzymes are proteins, and most such processes are chemical reactions. Within the enzyme, generally catalysis occurs at a localized site, called the active site.

<span class="mw-page-title-main">Pyruvate dehydrogenase</span> Class of enzymes

Pyruvate dehydrogenase is an enzyme that catalyzes the reaction of pyruvate and a lipoamide to give the acetylated dihydrolipoamide and carbon dioxide. The conversion requires the coenzyme thiamine pyrophosphate.

<span class="mw-page-title-main">Heme C</span> Chemical compound

Heme C is an important kind of heme.

<span class="mw-page-title-main">Pyridoxine 5′-phosphate oxidase</span> Class of enzymes

Pyridoxine 5′-phosphate oxidase is an enzyme, encoded by the PNPO gene, that catalyzes several reactions in the vitamin B6 metabolism pathway. Pyridoxine 5′-phosphate oxidase catalyzes the final, rate-limiting step in vitamin B6 metabolism, the biosynthesis of pyridoxal 5′-phosphate, the biologically active form of vitamin B6 which acts as an essential cofactor. Pyridoxine 5′-phosphate oxidase is a member of the enzyme class oxidases, or more specifically, oxidoreductases. These enzymes catalyze a simultaneous oxidation-reduction reaction. The substrate oxidase enzymes is hydroxlyated by one oxygen atom of molecular oxygen. Concurrently, the other oxygen atom is reduced to water. Even though molecular oxygen is the electron acceptor in these enzymes' reactions, they are unique because oxygen does not appear in the oxidized product.

<span class="mw-page-title-main">Serine dehydratase</span>

Serine dehydratase or L-serine ammonia lyase (SDH) is in the β-family of pyridoxal phosphate-dependent (PLP) enzymes. SDH is found widely in nature, but its structural and properties vary among species. SDH is found in yeast, bacteria, and the cytoplasm of mammalian hepatocytes. SDH catalyzes is the deamination of L-serine to yield pyruvate, with the release of ammonia.

<span class="mw-page-title-main">Cys/Met metabolism PLP-dependent enzyme family</span>

In molecular biology, the Cys/Met metabolism PLP-dependent enzyme family is a family of proteins including enzymes involved in cysteine and methionine metabolism which use PLP (pyridoxal-5'-phosphate) as a cofactor.

Ruma Banerjee is a professor of enzymology and biological chemistry at the University of Michigan Medical School. She is an experimentalist whose research has focused on unusual cofactors in enzymology.

References

  1. ↑ de Bolster, M.W.G. (1997). "Glossary of Terms Used in Bioinorganic Chemistry: Prosthetic groups". International Union of Pure and Applied Chemistry. Archived from the original on 2012-11-28. Retrieved 2007-10-30.
  2. ↑ Metzler DE (2001) Biochemistry. The chemical reactions of living cells, 2nd edition, Harcourt, San Diego.
  3. ↑ Nelson DL and Cox M.M (2000) Lehninger, Principles of Biochemistry, 3rd edition, Worth Publishers, New York
  4. ↑ Campbell MK and Farrell SO (2009) Biochemistry, 6th edition, Thomson Brooks/Cole, Belmont, California
  5. 1 2 Joosten V, van Berkel WJ (2007). "Flavoenzymes". Curr Opin Chem Biol. 11 (2): 195–202. doi:10.1016/j.cbpa.2007.01.010. PMID   17275397.
  6. ↑ Salisbury SA, Forrest HS, Cruse WB, Kennard O (1979). "A novel coenzyme from bacterial primary alcohol dehydrogenases". Nature. 280 (5725): 843–4. Bibcode:1979Natur.280..843S. doi:10.1038/280843a0. PMID   471057. S2CID   3094647.{{cite journal}}: CS1 maint: multiple names: authors list (link) PMID   471057
  7. ↑ Eliot AC, Kirsch JF (2004). "Pyridoxal phosphate enzymes: mechanistic, structural, and evolutionary considerations". Annu. Rev. Biochem. 73: 383–415. doi:10.1146/annurev.biochem.73.011303.074021. PMID   15189147.
  8. ↑ Jitrapakdee S, Wallace JC (2003). "The biotin enzyme family: conserved structural motifs and domain rearrangements". Curr. Protein Pept. Sci. 4 (3): 217–29. doi:10.2174/1389203033487199. PMID   12769720.
  9. ↑ Banerjee R, Ragsdale SW (2003). "The many faces of vitamin B12: catalysis by cobalamin-dependent enzymes". Annu. Rev. Biochem. 72: 209–47. doi:10.1146/annurev.biochem.72.121801.161828. PMID   14527323. S2CID   37393683.
  10. ↑ Frank RA, Leeper FJ, Luisi BF (2007). "Structure, mechanism and catalytic duality of thiamine-dependent enzymes". Cell. Mol. Life Sci. 64 (7–8): 892–905. doi:10.1007/s00018-007-6423-5. PMID   17429582. S2CID   20415735.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  11. ↑ Wijayanti N, Katz N, Immenschuh S (2004). "Biology of heme in health and disease". Curr. Med. Chem. 11 (8): 981–6. doi:10.2174/0929867043455521. PMID   15078160.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  12. ↑ Mendel RR, Hänsch R (2002). "Molybdoenzymes and molybdenum cofactor in plants". J. Exp. Bot. 53 (375): 1689–98. doi: 10.1093/jxb/erf038 . PMID   12147719.
  13. ↑ Mendel RR, Bittner F (2006). "Cell biology of molybdenum". Biochim. Biophys. Acta. 1763 (7): 621–35. doi:10.1016/j.bbamcr.2006.03.013. PMID   16784786.
  14. ↑ Bustamante J, Lodge JK, Marcocci L, Tritschler HJ, Packer L, Rihn BH (1998). "Alpha-lipoic acid in liver metabolism and disease". Free Radic. Biol. Med. 24 (6): 1023–39. doi:10.1016/S0891-5849(97)00371-7. PMID   9607614.{{cite journal}}: CS1 maint: multiple names: authors list (link)
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