Steroid: Difference between revisions
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{{about|the chemical family of lipids|the performance-enhancing substance|Anabolic steroid}} |
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[[Image:Steroid numbering.png|thumb|right|400px|[[IUPAC nomenclature|IUPAC]] recommended ring lettering (left) and atom numbering (right) of the steroid skeleton.<ref name="pmid2606099">{{cite journal | author = | title = IUPAC-IUB Joint Commission on Biochemical Nomenclature (JCBN). The nomenclature of steroids. Recommendations 1989 | journal = Eur. J. Biochem. | volume = 186 | issue = 3 | pages = 429–58 | year = 1989 | month = December | pmid = 2606099 | doi = 10.1111/j.1432-1033.1989.tb15228.x | url = http://www.chem.qmul.ac.uk/iupac/steroid/ }}</ref><ref name="IUPAC"/><br /><br />The four rings A-D form a [[sterane]] core.]] |
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[[Image:Lanosterol-3D-sticks.png|thumb|right|400px|Stick model of the steroid [[lanosterol]]. The total number of carbons (30) reflects its [[triterpenoid]] origin.]] |
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A '''steroid''' is a type of [[organic compound]] that contains a specific arrangement of four rings that are joined to each other. Examples of steroids include [[cholesterol]], the sex hormones [[estradiol]] and [[testosterone]], and the [[anti-inflammatory]] drug [[dexamethasone]]. |
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The [[sterane]] core of steroids is composed of seventeen [[carbon]] atoms bonded together to form four fused rings: three [[cyclohexane]] rings (designated as rings A, B, and C in the figure to the right) and one [[cyclopentane]] ring (the D ring). The steroids vary by the functional groups attached to these rings and by the [[oxidation]] state of the rings. [[Sterol]]s are special forms of steroids, with a [[hydroxyl]] group at position-3 and a skeleton derived from [[cholestane]].<ref name="IUPAC">{{cite journal | journal = [[Pure & Appl. Chem.]] | volume = 61 | issue = 10 | pages = 1783–1822 | year = 1989 | title = Nomenclature of Steroids (Recommendations 1989) | author = G. P. Moss | doi = 10.1351/pac198961101783}} [http://iupac.org/publications/pac/61/10/1783/pdf/.pdf PDF]</ref> |
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Hundreds of distinct steroids are found in [[plant]]s, [[animal]]s, and [[Fungus|fungi]]. All steroids are made in cells either from the sterols [[lanosterol]] (animals and fungi) or from [[cycloartenol]] (plants). Both lanosterol and cycloartenol are derived from the cyclization of the [[triterpene]] [[squalene]].<ref>[http://www.chem.qmul.ac.uk/iubmb/enzyme/reaction/terp/lanost.html Lanosterol biosynthesis<!-- Bot generated title -->]</ref> |
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==Classification== |
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===Taxonomical/Functional=== |
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Some of the common categories of steroids: |
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*Animal steroids |
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**[[Insect]] steroids |
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***Ecdysteroids such as [[ecdysterone]] |
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**[[Vertebrate]] steroids |
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***[[Steroid hormone]]s |
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****[[Sex steroid]]s are a subset of [[sex hormone]]s that produce [[sexual differentiation|sex differences]] or support [[reproduction]]. They include [[androgen]]s, [[estrogen]]s, and [[progestagen]]s. |
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****[[Corticosteroid]]s include [[glucocorticoid]]s and [[mineralocorticoid]]s. Glucocorticoids regulate many aspects of [[metabolism]] and [[immune system|immune function]], whereas mineralocorticoids help maintain blood volume and control [[kidney|renal]] excretion of [[electrolyte]]s. Most medical 'steroid' [[drug]]s are corticosteroids. |
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****[[Anabolic steroid]]s are a class of steroids that interact with androgen receptors to increase muscle and bone synthesis. There are natural and synthetic anabolic steroids. In popular language, the word "steroids" usually refers to anabolic steroids. |
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***[[Cholesterol]], which modulates the fluidity of [[cell membranes]] and is the principal constituent of the plaques implicated in [[atherosclerosis]]. |
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*Plant steroids |
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**[[Phytosterol]]s |
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**[[Brassinosteroid]]s |
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*Fungus steroids |
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**[[Ergosterol]]s |
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===Structural=== |
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It is also possible to classify steroids based upon their chemical composition. One example of how [[Medical Subject Headings|MeSH]] performs this classification is available at [[Wikipedia:MeSH D04#MeSH D04.808 --- steroids|the Wikipedia MeSH catalog]]. Examples from this classification include: |
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{| class="wikitable" |
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|- |
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! align="center" | Class |
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! align="center" | Examples |
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! align="center" | Number of carbon atoms |
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|- |
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| align="center" | [[Cholestane]]s |
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| align="center" | [[cholesterol]] |
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| align="center" | 27 |
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|- |
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| align="center" | [[Cholane]]s |
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| align="center" | [[cholic acid]] |
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| align="center" | 24 |
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|- |
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| align="center" | [[Pregnane]]s |
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| align="center" | [[progesterone]] |
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| align="center" | 21 |
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|- |
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| align="center" | [[Androstane]]s |
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| align="center" | [[testosterone]] |
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| align="center" | 19 |
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|- |
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| align="center" | [[Estrane]]s |
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| align="center" | [[estradiol]] |
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| align="center" | 18 |
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|- |
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|} |
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''[[Gonane]]'' (or steroid nucleus) is the hypothetic parent (17-carbon tetracyclic) hydrocarbon molecule without any [[alkyl]] sidechains.<ref>[http://www.britannica.com/facts/5/223074/gonane-as-discussed-in-steroid-chemical-compound britannica.com > Facts about gonane: steroids, as discussed in steroid (chemical compound): Steroid numbering system and nomenclature] Retrieved on Feb 13, 2010</ref> |
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==Metabolism== |
==Metabolism== |
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Steroids include [[estrogen]], [[cortisol]], [[progesterone]], and [[testosterone]]. Estrogen and progesterone are made primari* steroidogenesis – the interconversion of different types of steroids |
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Steroids include [[estrogen]], [[cortisol]], [[progesterone]], and [[testosterone]]. Estrogen and progesterone are made primarily in the [[ovary]] and in the [[placenta]] during pregnancy, and [[testosterone]] in the [[testes]]. Testosterone is also converted into estrogen to regulate the supply of each, in the bodies of both females and males. Certain [[neurons]] and [[glia]] in the [[central nervous system]] (CNS) express the [[enzymes]] that are required for the local synthesis of [[pregnane]] [[neurosteroids]], either [[de novo synthesis|''de novo'']] or from peripherally-derived sources. The rate-limiting step of steroid synthesis is the conversion of [[cholesterol]] to [[pregnenolone]], which occurs inside the [[mitochondrion]].<ref name=Rossier>{{cite journal | title=T channels and steroid biosynthesis: in search of a link with mitochondria | author=Rossier MF | journal=Cell Calcium. | date=2006 | volume=40 | issue=2 | pages=155–64 | pmid=16759697 | doi=10.1016/j.ceca.2006.04.020 }}</ref> |
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[[Image:Sterol synthesis.svg|thumb|right|350px|Simplified version of latter part of steroid synthesis pathway, where the intermediates [[isopentenyl pyrophosphate]] (IPP) and [[dimethylallyl pyrophosphate]] (DMAPP) form [[geranyl pyrophosphate]] (GPP), [[squalene]] and, finally, [[lanosterol]], the first steroid in the pathways. Some intermediates are omitted for clarity.]] |
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'''Steroid metabolism''' is the complete set of [[chemical reactions]] in organisms that produce, modify, and consume steroids. These [[metabolic pathway]]s include: |
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* steroid synthesis – the manufacture of steroids from simpler precursors |
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* steroidogenesis – the interconversion of different types of steroids |
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* steroid degradation. |
* steroid degradation. |
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*[[estrogens]] and [[progesterone]] |
*[[estrogens]] and [[progesterone]] |
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*[[corticoids]] |
*[[corticoids]] |
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*peasssssssssasdasdasdasdasdasd |
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**[[cortisol]] |
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**[[aldosterone]] |
**[[aldosterone]] |
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===Elimination=== |
===Elimination=== |
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Steroids are oxidized mainly by [[cytochrome P450|cytochrome P450 oxidase]] enzymes, such as [[CYP3A4]]. These reactions introduce oxygen into the steroid ring and allows the structure to be broken up by other enzymes, to form [[bile acid]]s as final products.<ref>{{cite journal |author=Pikuleva IA |title=Cytochrome P450s and cholesterol homeostasis |journal=Pharmacol. Ther. |volume=112 |issue=3 |pages=761–73 |year=2006 |pmid=16872679 |doi=10.1016/j.pharmthera.2006.05.014}}</ref> These bile acids can then be eliminated through secretion from the [[liver]] in the [[bile]].<ref>{{cite journal |author=Zollner G, Marschall HU, Wagner M, Trauner M |title=Role of nuclear receptors in the adaptive response to bile acids and cholestasis: pathogenetic and therapeutic considerations |journal=Mol. Pharm. |volume=3 |issue=3 |pages=231–51 |year=2006 |pmid=16749856 |doi=10.1021/mp060010s}}</ref> The expression of this oxidase gene can be upregulated by the steroid sensor [[PXR]] when there is a high blood concentration of steroids.<ref name="Kliewer">{{cite journal |author=Kliewer S, Goodwin B, Willson T |title=The nuclear pregnane X receptor: a key regulator of xenobiotic metabolism |journal=Endocr. Rev. |volume=23 |issue=5 |pages=687–702 |year=2002 |pmid=12372848 |doi=10.1210/er.2001-0038}}</ref> |
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==See also== |
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*[[Batrachotoxin]] |
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*[[List of steroid abbreviations]] |
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==References== |
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{{reflist}} |
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==Further reading== |
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{{refbegin}} |
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* {{cite journal | author = Simons SS | title = What goes on behind closed doors: physiological versus pharmacological steroid hormone actions | journal = Bioessays | volume = 30 | issue = 8 | pages = 744–56 | year = 2008 | month = August | pmid = 18623071 | doi = 10.1002/bies.20792 | url = | issn = | pmc = 2742386 }} |
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{{refend}} |
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==External links== |
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* [http://www.chem.qmul.ac.uk/iupac/steroid/ Nomenclature of Steroids Home Page] at Queen Mary University of London. |
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* [http://arbl.cvmbs.colostate.edu/hbooks/pathphys/endocrine/basics/steroidogenesis.html Steroidogenesis] |
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{{Steroids}} |
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{{Metabolism}} |
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[[Category:Metabolic pathways]] |
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[[Category:Steroids|*]] |
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[[ar:ستيرويد]] |
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[[bg:Стероид]] |
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[[ca:Esteroide]] |
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[[cs:Steroidy]] |
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[[de:Steroide]] |
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[[et:Steroidid]] |
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[[es:Esteroide]] |
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[[eo:Steroido]] |
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[[eu:Esteroide]] |
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[[fa:استروئید]] |
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[[fr:Stéroïde]] |
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[[ga:Stéaróideach]] |
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[[ko:스테로이드]] |
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[[hr:Steroidi]] |
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[[id:Steroid]] |
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[[it:Steroide]] |
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[[he:סטרואיד]] |
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[[ht:Estewoyid]] |
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[[ms:Steroid]] |
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[[nl:Steroïde]] |
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[[ja:ステロイド]] |
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[[no:Steroid]] |
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[[oc:Esteroïde]] |
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[[pl:Steroidy]] |
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[[pt:Esteroide]] |
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[[ro:Steroid]] |
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[[ru:Стероиды]] |
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[[simple:Steroid]] |
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[[sk:Steroid]] |
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[[sr:Стероиди]] |
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[[sh:Steroidi]] |
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[[su:Stéroid]] |
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[[fi:Steroidi]] |
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[[sv:Steroid]] |
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[[th:สเตอรอยด์]] |
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[[tr:Steroid]] |
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[[uk:Стероїди]] |
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[[zh:甾族化合物]] |
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Revision as of 16:20, 10 November 2010
Metabolism
Steroids include estrogen, cortisol, progesterone, and testosterone. Estrogen and progesterone are made primari* steroidogenesis – the interconversion of different types of steroids
- steroid degradation.
Steroid biosynthesis
Steroid biosynthesis is an anabolic metabolic pathway that produces steroids from simple precursors. This pathway is carried out in different ways in animals than in many other organisms, making the pathway a common target for antibiotics and other anti-infective drugs. In addition, steroid metabolism in humans is the target of cholesterol-lowering drugs such as statins.
It starts in the mevalonate pathway in humans, with Acetyl-CoA as building blocks, which form DMAPP and IPP[1]. In following steps, DMAPP and IPP form lanosterol, the first steroid. Further modification belongs to the succeeding steroidogenesis.
Mevalonate pathway
The mevalonate pathway or HMG-CoA reductase pathway starts with and ends with dimethylallyl pyrophosphate (DMAPP) and isopentenyl pyrophosphate (IPP).
Regulation and feedback
Several key enzymes can be activated through DNA transcriptional regulation on activation of SREBP (Sterol Regulatory Element-Binding Protein-1 and -2). This intracellular sensor detects low cholesterol levels and stimulates endogenous production by the HMG-CoA reductase pathway, as well as increasing lipoprotein uptake by up-regulating the LDL receptor. Regulation of this pathway is also achieved by controlling the rate of translation of the mRNA, degradation of reductase and phosphorylation.
Pharmacology
A number of drugs target the mevalonate pathway:
- Statins (used for elevated cholesterol levels)
- Bisphosphonates (used in treatment of various bone-degenerative diseases)
Plants and bacteria
In plants and bacteria, the non-mevalonate pathway uses pyruvate and glyceraldehyde 3-phosphate as substrates.[2][3]
DMAPP to lanosterol
Isopentenyl pyrophosphate and dimethylallyl pyrophosphate donate isoprene units, which are assembled and modified to form terpenes and isoprenoids[3], which are a large class of lipids that include the carotenoids, and form the largest class of plant natural products.[4]
Here, the isoprene units are joined together to make squalene and then folded up and formed into a set of rings to make lanosterol.[5] Lanosterol can then be converted into other steroids such as cholesterol and ergosterol.[5][6]
Steroidogenesis
Steroidogenesis is the biological process by which steroids are generated from cholesterol and transformed into other steroids. The pathways of steroidogenesis differ between different species, but the pathways of human steroidogenesis are shown in the figure.
Products of steroidogenesis include:
- androgens
- estrogens and progesterone
- corticoids
- peasssssssssasdasdasdasdasdasd
Elimination
- ^ Grochowski L, Xu H, White R (2006). "Methanocaldococcus jannaschii uses a modified mevalonate pathway for biosynthesis of isopentenyl diphosphate". J Bacteriol. 188 (9): 3192–8. doi:10.1128/JB.188.9.3192-3198.2006. PMC 1447442. PMID 16621811.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Lichtenthaler H (1999). "The 1-Dideoxy-D-xylulose-5-phosphate pathway of isoprenoid biosynthesis in plants". Annu Rev Plant Physiol Plant Mol Biol. 50: 47–65. doi:10.1146/annurev.arplant.50.1.47. PMID 15012203.
- ^ a b Kuzuyama T, Seto H (2003). "Diversity of the biosynthesis of the isoprene units". Nat Prod Rep. 20 (2): 171–83. doi:10.1039/b109860h. PMID 12735695.
- ^ Dubey V, Bhalla R, Luthra R (2003). "An overview of the non-mevalonate pathway for terpenoid biosynthesis in plants" (PDF). J Biosci. 28 (5): 637–46. doi:10.1007/BF02703339. PMID 14517367.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b Schroepfer G (1981). "Sterol biosynthesis". Annu Rev Biochem. 50: 585–621. doi:10.1146/annurev.bi.50.070181.003101. PMID 7023367.
- ^ Lees N, Skaggs B, Kirsch D, Bard M (1995). "Cloning of the late genes in the ergosterol biosynthetic pathway of Saccharomyces cerevisiae—a review". Lipids. 30 (3): 221–6. doi:10.1007/BF02537824. PMID 7791529.
{{cite journal}}: CS1 maint: multiple names: authors list (link)