View source for 5α-Reductase

{{enzyme
| Name = 3-Oxo-5α-steroid 4-dehydrogenase
| EC_number = 1.3.1.22
| CAS_number = 9036-43-5
| IUBMB_EC_number = 1/3/99/5
| GO_code = 0003865
| image = 
| width = 
| caption = 
}}
{{infobox protein
| Name = [[SRD5A1|Steroid-5α-reductase, alpha polypeptide 1]]
| caption = 
| image = 
| width = 
| HGNCid = 11284
| Symbol = [[SRD5A1]]
| AltSymbols = 
| EntrezGene = 6715
| OMIM = 184753
| RefSeq = NM_001047
| UniProt = P18405
| PDB = 
| ECnumber = 1.3.1.22
| Chromosome = 5
| Arm = p
| Band = 15
| LocusSupplementaryData = 
}}
{{infobox protein
| Name = [[SRD5A2|Steroid-5α-reductase, alpha polypeptide 2]]
| caption = 
| image = 
| width = 
| HGNCid = 11285
| Symbol = [[SRD5A2]]
| AltSymbols = 
| EntrezGene = 6716
| OMIM = 607306
| RefSeq = NM_000348
| UniProt = P31213
| PDB = 
| ECnumber = 1.3.1.22
| Chromosome = 2
| Arm = p
| Band = 23
| LocusSupplementaryData = 
}}

[[File:Steroidogenesis.svg|thumb|235px|right|[[Steroidogenesis]], showing both actions of 5α-reductase at bottom center.]]
'''5α-reductases''', also known as '''3-oxo-5α-steroid 4-dehydrogenases''', are [[enzyme]]s involved in steroid metabolism. They participate in 3 [[metabolism|metabolic pathways]]: [[bile acid]] biosynthesis, [[androgen]] and [[estrogen]] metabolism.  There are three [[isoenzymes]] of 5α-reductase, [[SRD5A1]], [[SRD5A2]], and [[SRD5A3]], which vary in different tissues with age.

5α-Reductases [[catalysis|catalyze]] the following [[chemical reaction]]:

:a 3-oxo-5α-steroid + acceptor {{eqm}} a 3-oxo-Δ<sup>4</sup>-steroid + reduced acceptor

Thus, the two [[substrate (biochemistry)|substrates]] of these enzymes are a 3-oxo-5α-steroid and acceptor, whereas its two [[product (chemistry)|products]] are 3-oxo-Δ4-steroid and a reduced acceptor.
For example: 

:[[dihydrotestosterone]] + NADP<sup>+</sup> <math>\rightleftharpoons</math> [[testosterone]] + NADPH + H<sup>+</sup>

==Production and activity==
The enzyme is produced in many tissues in both males and females, in the reproductive tract, testes and ovaries,<ref name="pmid18473173">{{cite journal |vauthors=Pinna G, Agis-Balboa RC, Pibiri F, Nelson M, Guidotti A, Costa E |title=Neurosteroid biosynthesis regulates sexually dimorphic fear and aggressive behavior in mice |journal=Neurochem. Res. |volume=33 |issue=10 |pages=1990–2007 |date=October 2008 |pmid=18473173 |doi=10.1007/s11064-008-9718-5}}</ref> [[skin]], [[seminal vesicles]], [[prostate]], [[epididymis]] and many organs,<ref name = "Yamana_2010">{{cite journal |vauthors=Yamana K, Labrie F, Luu-The V | title = Human type 3 5α-reductase is expressed in peripheral tissues at higher levels than types 1 and 2 and its activity is potently inhibited by finasteride and dutasteride | journal = Hormone Molecular Biology and Clinical Investigation |date=January 2010 | volume = 2 | issue = 3 | doi = 10.1515/hmbci.2010.035 }}</ref> including the [[Nervous System]].<ref name="pmid16984997">{{cite journal |vauthors=Agís-Balboa RC, Pinna G, Zhubi A, Maloku E, Veldic M, Costa E, Guidotti A |title=Characterization of brain neurons that express enzymes mediating neurosteroid biosynthesis. |journal=Proc Natl Acad Sci U S A |volume=103 |issue=39 |pages=14602–7 |date=September 2006 |pmid=16984997 |doi=10.1073/pnas.0606544103 |pmc=1600006}}</ref><ref name="pmid18003893">{{cite journal |vauthors=Agís-Balboa RC, Pinna G, Pibiri F, Kadriu B, Costa E, Guidotti A |title=Down-regulation of neurosteroid biosynthesis in corticolimbic circuits mediates social isolation-induced behavior in mice. |journal=Proc Natl Acad Sci U S A |volume=104 |issue=47 |pages=18736–41 |date=November 2007 |pmid=18003893 |doi=10.1073/pnas.0709419104 |pmc=2141846}}</ref> There are three [[isoenzyme]]s of 5α-reductase: steroid 5α-reductase 1, 2, and 3 ([[SRD5A1]], [[SRD5A2]] and [[SRD5A3]]).<ref name="Yamana_2010"/><ref name="pmid12606426">{{cite journal |vauthors=Killian J, Pratis K, Clifton RJ, Stanton PG, Robertson DM, O'Donnell L | title = 5alpha-reductase isoenzymes 1 and 2 in the rat testis during postnatal development | journal = Biol. Reprod. | volume = 68 | issue = 5 | pages = 1711–8 |date=May 2003 | pmid = 12606426 | doi = 10.1095/biolreprod.102.009142 }}</ref><ref name="pmid15941927">{{cite journal |vauthors=Thiele S, Hoppe U, Holterhus PM, Hiort O | title = Isoenzyme type 1 of 5alpha-reductase is abundantly transcribed in normal human genital skin fibroblasts and may play an important role in masculinization of 5alpha-reductase type 2 deficient males | journal = Eur. J. Endocrinol. | volume = 152 | issue = 6 | pages = 875–80 |date=June 2005 | pmid = 15941927 | doi = 10.1530/eje.1.01927 }}</ref><ref name="godoy">{{cite journal |vauthors=Godoy A, Kawinski E, Li Y, Oka D, Alexiev B, Azzouni F, Titus MA, Mohler JL | title = 5α-reductase type 3 expression in human benign and malignant tissues: a comparative analysis during prostate cancer progression | journal = Prostate | volume = 71 | issue = 10 | pages = 1033–46 |date=July 2011 | pmid = 21557268 | doi = 10.1002/pros.21318 | pmc = 4295561 }}</ref>

5α-Reductases act on 3-oxo (3-keto), Δ<sup>4,5</sup> C19/C21 steroids as its substrates. “3-keto” refers to the double bond of the third carbon to oxygen. Carbons 4 and 5 also have a double bond, represented by 'Δ<sup>4,5</sup>'. The reaction involves a stereospecific and permanent break of the Δ<sup>4,5</sup> with the help of NADPH as a cofactor. A hydride anion (H−) is also placed on the α face at the fifth carbon, and a proton on the β face at carbon 4.<ref name="Azz">{{cite journal |vauthors=Azzouni F, Godoy A, Li Y, Mohler J | title = The 5 alpha-reductase isozyme family: a review of basic biology and their role in human diseases | journal = Adv Urol | volume = 2012 | issue = | pages = 530121 | year = 2012 | pmid = 22235201 | pmc = 3253436 | doi = 10.1155/2012/530121 }}</ref>

==Distribution with age==
{{expert needed|date=September 2016}}
5α-R1 is expressed in fetal scalp and nongenital skin of the back, anywhere from 5 to 50 times less than in the adult. 5α-R2 is expressed in fetal prostates similar to adults. 5α-R1 is expressed mainly in the [[epithelium]] and 5α-R2 the stroma of the fetal prostate. Scientists looked for 5α-R2 expression in fetal liver, adrenal, testis, ovary, brain, scalp, chest, and genital skin, using immunoblotting, and were only able to find it in genital skin.<ref name="Azz"/>

After birth, the 5α-R1 is expressed in more locations, including the liver, skin, scalp and prostate. 5α-R2 is expressed in prostate, seminal vesicles, epididymis, liver, and to a lesser extent the scalp and skin. Hepatic expression of both 5α-R1 and 2 is immediate, but disappears in the skin and scalp at month 18. Then, at puberty, only  5α-R1 is reexpressed in the skin and scalp.

5α-R1 and 5α-R2 appear to be expressed in the prostate in male fetuses and throughout postnatal life. In adulthood, 5α-R1-3 is ubiquitously expressed. 5α-R1 and 5α-R2 are also expressed, although to different degrees in liver, genital and nongenital skin, prostate, epididymis, seminal vesicle, testis, ovary, uterus, kidney, exocrine pancreas, and the brain.<ref name="pmid16984997"/><ref name="Azz"/>

==Substrates==
Specific substrates include [[testosterone]], [[progesterone]], [[androstenedione]],<ref name="pmid21361868">{{cite journal | vauthors = Paba S, Frau R, Godar SC, Devoto P, Marrosu F, Bortolato M | title = Steroid 5α-reductase as a novel therapeutic target for schizophrenia and other neuropsychiatric disorders | journal = Curr. Pharm. Des. | volume = 17 | issue = 2 | pages = 151–67 | year = 2011 | pmid = 21361868 | doi = 10.2174/138161211795049589| url = }}</ref> [[epitestosterone]], [[cortisol]], [[aldosterone]], and [[deoxycorticosterone]]. Outside of dihydrotestosterone, much of the physiological role of 5α-reduced steroids is unknown.<ref name="Azz"/> Beyond reducing testosterone to dihydrotestosterone, 5alpha-reductase enzyme isoforms I and II reduce progesterone to dihydroprogesterone (DHP) and deoxycorticosterone to dihydrodeoxycorticosterone (DHDOC). In vitro and animal models suggest subsequent 3alpha-reduction of DHT, DHP and DHDOC lead to steroid metabolites with effects on cerebral function achieved by enhancing [[Gamma-Aminobutyric acid|GABA]]<nowiki/>ergic inhibition. These neuroactive steroid derivatives enhance GABA via allosteric modulation at GABA(A) receptors and have anticonvulsant, antidepressant and anxiolytic effects, and also alter sexual and alcohol related behavior.<ref>{{cite journal | vauthors = Finn DA, Beadles-Bohling AS, Beckley EH, Ford MM, Gililland KR, Gorin-Meyer RE, Wiren KM | title = A new look at the 5alpha-reductase inhibitor finasteride | journal = CNS Drug Reviews | volume = 12 | issue = 1 | pages = 53-76 | year = 2006 | pmid = 16834758 | pmc =  | doi = 10.1111/j.1527-3458.2006.00053.x }}</ref> 5α-dihydrocortisol is present in the [[aqueous humor]] of the eye, is synthesized in the [[Lens (anatomy)|lens]], and might help make the aqueous humor itself.<ref name="Cort">{{cite journal |vauthors=Weinstein BI, Kandalaft N, Ritch R, Camras CB, Morris DJ, Latif SA, Vecsei P, Vittek J, Gordon GG, Southren AL | title = 5 alpha-dihydrocortisol in human aqueous humor and metabolism of cortisol by human lenses in vitro | journal = Invest. Ophthalmol. Vis. Sci. | volume = 32 | issue = 7 | pages = 2130–5 |date=June 1991 | pmid = 2055703 | doi = }}</ref> [[Allopregnanolone]] and [[Tetrahydrodeoxycorticosterone|THDOC]] are [[neurosteroids]], with the latter having effects on the susceptibility of animals to seizures. In socially isolated mice, 5α-R1 is specifically down-regulated in glutamatergic pyramidal neurons that converge on the amygdala from cortical and hippocampal regions.  This down-regulation may account for the appearance of behavioral disorders such as anxiety, aggression, and cognitive dysfunction.<ref name="pmid16984997"/><ref name="pmid18003893"/> 5α-dihydroaldosterone is a potent [[Natriuresis|antinatriuretic]] agent, although different from [[aldosterone]]. Its formation in the kidney is enhanced by restriction of dietary salt, suggesting it may help retain sodium as follows:<ref name="Kenyon_1983">{{cite journal | vauthors = Kenyon CJ, Brem AS, McDermott MJ, Deconti GA, Latif SA, Morris DJ | title = Antinatriuretic and kaliuretic activities of the reduced derivatives of aldosterone | journal = Endocrinology | volume = 112 | issue = 5 | pages = 1852–6 | date = May 1983 | pmid = 6403339 | doi = 10.1210/endo-112-5-1852 }}</ref>

:::  ''<chem>{Substrate} + {NADPH} + H+   ->  {5\alpha-substrate} + NADP+</chem>''

5α-DHP is a major hormone in circulation of normal cycling and pregnant women.<ref name="pmid914969">{{cite journal |vauthors=Milewich L, Gomez-Sanchez C, Crowley G, Porter JC, Madden JD, MacDonald PC | title = Progesterone and 5alpha-pregnane-3,20-dione in peripheral blood of normal young women: Daily measurements throughout the menstrual cycle | journal = J. Clin. Endocrinol. Metab. | volume = 45 | issue = 4 | pages = 617–22 |date=October 1977 | pmid = 914969 | doi =10.1210/jcem-45-4-617 }}</ref>

===Testosterone===
5α-Reductase is most known for converting [[testosterone]], the male [[sex hormone]], into the more potent [[dihydrotestosterone]]:
<gallery>
 Image:Testosteron.svg|[[Testosterone]].
 Image:Androstanolone.svg|[[Dihydrotestosterone]]
</gallery>

The major difference is the Δ<sup>4,5</sup> double-bond on the A (leftmost) ring. The other differences between the diagrams are unrelated to structure.

===List of conversions===
The following reactions are known to be catalyzed by 5α-reductase:<ref name="pmid21361868" />

* [[Cholestenone]] → [[5α-Cholestanone]]
* [[Progesterone]] → [[5α-Dihydroprogesterone]]
* [[3α-Dihydroprogesterone]] → [[Allopregnanolone]]
* [[3β-Dihydroprogesterone]] → [[Isopregnanolone]]
* [[Deoxycorticosterone]] → [[5α-Dihydrodeoxycorticosterone]]
* [[Corticosterone]] → [[5α-Dihydrocorticosterone]]
* [[Cortisol]] → [[5α-Dihydrocortisol]]
* [[Aldosterone]] → [[5α-Dihydroaldosterone]]
* [[Androstenedione]] → [[5α-Androstanedione]]
* [[Testosterone]] → [[5α-Dihydrotestosterone]]

==Inhibition==
{{Main article|5α-Reductase inhibitor}}
The mechanism of 5α reductase inhibition is complex, but involves the binding of NADPH to the enzyme followed by the substrate. [[5α-reductase inhibitor]] drugs are used in [[benign prostatic hyperplasia]], [[prostate cancer]], [[pattern hair loss]] (androgenetic alopecia), and [[hormone replacement therapy (male-to-female)|hormone replacement therapy]] for [[transgender women]].

Inhibition of the enzyme can be classified into two categories: steroidal, which are irreversible, and nonsteroidal. There are more steroidal inhibitors, with examples including finasteride (MK-906), dutasteride (GG745), 4-MA, turosteride, MK-386, MK-434, and MK-963. Researchers have pursued synthesis of nonsteroidals to inhibit 5α-reductase due to the undesired side effects of steroidals. The most potent and selective inhibitors of 5α-R1 are found in this class, and include benzoquinolones, nonsteroidal aryl acids, butanoid acid derivatives, and more recognizably, [[polyunsaturated fatty acid]]s (especially [[linolenic acid]]), [[zinc]], and [[green tea]].<ref name="Azz"/> [[Riboflavin]] was also identified as a 5α-reductase inhibitor .<ref name="pmid2276981">{{cite journal |vauthors=Nakayama O, Yagi M, Kiyoto S, Okuhara M, Kohsaka M | title = Riboflavin, a testosterone 5 alpha-reductase inhibitor | journal = J. Antibiot. | volume = 43 | issue = 12 | pages = 1615–6 |date=December 1990 | pmid = 2276981 | doi = 10.7164/antibiotics.43.1615 }}</ref>

Additionally, it has been claimed that [[alfatradiol]] works through this mechanism of activity (5α-reductase), as well as the [[Ganoderic acid]]s in [[lingzhi mushroom]], and the [[Saw Palmetto]].

Inhibition of 5α-reductase results in decreased conversion of testosterone to DHT, leading to increased testosterone and [[estradiol]]. Other enzymes compensate to a degree for the absent conversion, specifically with local expression at the skin of reductive [[17β-hydroxysteroid dehydrogenase]], oxidative [[3α-hydroxysteroid dehydrogenase]], and [[3β-hydroxysteroid dehydrogenase]] enzymes.<ref name="pmid11399532">{{cite journal | author = Andersson S | title = Steroidogenic enzymes in skin | journal = Eur J Dermatol | volume = 11 | issue = 4 | pages = 293–5 | year = 2001 | pmid = 11399532 | doi = }}</ref>

[[Gynecomastia]], [[erectile dysfunction]], impaired cognitive function,  [[fatigue (medical)|fatigue]], [[hypoglycemia]], impaired liver function, [[constipation]], and [[Depression (mood)|depression]], are only a few of the possible side-effects of 5α-reductase inhibition. Long term side effects, that continued even after discontinuation of the drug have been reported.<ref name="pmid21418145">{{cite journal |vauthors=Irwig MS, Kolukula S | title = Persistent sexual side effects of finasteride for male pattern hair loss | journal = J Sex Med | volume = 8 | issue = 6 | pages = 1747–53 |date=June 2011 | pmid = 21418145 | doi = 10.1111/j.1743-6109.2011.02255.x }}</ref>

===Finasteride===
[[Finasteride]] inhibits two 5α-reductase isoenzymes (II and III), while [[dutasteride]] inhibits all three.<ref name="Yamana_2010"/> Finasteride potently inhibits 5α-R2 at a mean inhibitory concentration IC<sub>50</sub> of 69 nM, but is less effective with 5α-R1 till an IC<sub>50</sub> of 360 nM.<ref name="pmid8117686">{{cite journal |vauthors=Tian G, Stuart JD, Moss ML, Domanico PL, Bramson HN, Patel IR, Kadwell SH, Overton LK, Kost TA, Mook RA | title = 17 beta-(N-tert-butylcarbamoyl)-4-aza-5 alpha-androstan-1-en-3-one is an active site-directed slow time-dependent inhibitor of human steroid 5 alpha-reductase 1 | journal = Biochemistry | volume = 33 | issue = 8 | pages = 2291–6 |date=March 1994 | pmid = 8117686 | doi =10.1021/bi00174a041 }}</ref> Finasteride decreases mean serum level of DHT by 71% after 6 months,<ref name="pmid1371291">{{cite journal |vauthors=McConnell JD, Wilson JD, George FW, Geller J, Pappas F, Stoner E | title = Finasteride, an inhibitor of 5 alpha-reductase, suppresses prostatic dihydrotestosterone in men with benign prostatic hyperplasia | journal = J. Clin. Endocrinol. Metab. | volume = 74 | issue = 3 | pages = 505–8 |date=March 1992 | pmid = 1371291 | doi =10.1210/jc.74.3.505 }}</ref> and was shown in vitro to inhibit 5α-R3 at a similar potency to 5α-R2 in transfected cell lines.<ref name="Yamana_2010" />

===Dutasteride===
[[Dutasteride]] inhibits 5α-reductase isoenzymes type 1 and 2 better than finasteride, leading to a more complete reduction in DHT at 24 weeks (94.7% versus 70.8%).<ref name="pmid15126539">{{cite journal |vauthors=Clark RV, Hermann DJ, Cunningham GR, Wilson TH, Morrill BB, Hobbs S | title = Marked suppression of dihydrotestosterone in men with benign prostatic hyperplasia by dutasteride, a dual 5alpha-reductase inhibitor | journal = J. Clin. Endocrinol. Metab. | volume = 89 | issue = 5 | pages = 2179–84 |date=May 2004 | pmid = 15126539 | doi =10.1210/jc.2003-030330 }}</ref> It also reduces intraprostatic DHT 97% in men with prostate cancer at 5&nbsp;mg/day over three months.<ref name="pmid15310997">{{cite journal |vauthors=Andriole GL, Humphrey P, Ray P, Gleave ME, Trachtenberg J, Thomas LN, Lazier CB, Rittmaster RS | title = Effect of the dual 5alpha-reductase inhibitor dutasteride on markers of tumor regression in prostate cancer | journal = J. Urol. | volume = 172 | issue = 3 | pages = 915–9 |date=September 2004 | pmid = 15310997 | doi = 10.1097/01.ju.0000136430.37245.b9 }}</ref> A second study with 3.5&nbsp;mg/day for 4 months decreased intraprostatic DHT even further by 99%.<ref name="pmid16927304">{{cite journal |vauthors=Gleave M, Qian J, Andreou C, Pommerville P, Chin J, Casey R, Steinhoff G, Fleshner N, Bostwick D, Thomas L, Rittmaster R | title = The effects of the dual 5alpha-reductase inhibitor dutasteride on localized prostate cancer--results from a 4-month pre-radical prostatectomy study | journal = Prostate | volume = 66 | issue = 15 | pages = 1674–85 |date=November 2006 | pmid = 16927304 | doi = 10.1002/pros.20499 }}</ref> The suppression of DHT in vivo, and the report that dutasteride inhibits 5α-R3 in vitro<ref name="pmid2606099">{{cite journal | author = Moss GP | 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 |date=December 1989 | pmid = 2606099 | doi = 10.1111/j.1432-1033.1989.tb15228.x| url = }}</ref> suggest that dutasteride may be a triple 5α reductase inhibitor.<ref name="Azz"/>

==Congenital deficiencies==
{{Main article|5α-Reductase deficiency}}

===5α-Reductase 1===
5α-Reductase type 1 inactivated male mice have reduced bone mass and forelimb muscle grip strength, which has been proposed to be due to lack of 5α-reductase type 1 expression in bone and muscle.<ref name="pmid21731732">{{cite journal | vauthors = Windahl SH, Andersson N, Börjesson AE, Swanson C, Svensson J, Movérare-Skrtic S, Sjögren K, Shao R, Lagerquist MK, Ohlsson C | title = Reduced bone mass and muscle strength in male 5α-reductase type 1 inactivated mice | journal = PLoS ONE | volume = 6 | issue = 6 | pages = e21402 | year = 2011 | pmid = 21731732 | pmc = 3120862 | doi = 10.1371/journal.pone.0021402 | editor1-last = Vanacker | editor1-first = Jean-Marc }}</ref> In 5 alpha reductase type 2 deficient males, the type 1 isoenzyme is thought to be responsible for their virilization at puberty.<ref name="pmid15941927" />

===5α-Reductase 2===
The second isoenzyme of 5α reductase is deficient in the classic [[intersex]] condition (''[[pseudovaginal perineoscrotal hypospadias]]''), or [[5α-reductase deficiency]]. It was first discovered in indigenous cultures of [[Papua, New Guinea]], where children were born with feminine genitalia in the absence of endogenous DHT during pregnancy, but with the surge of testosterone during adolescence, changed to males at puberty. Because of this change at puberty, the condition is also sometimes called "[[guevedoche]]."<ref name=guevodoche>{{cite book|last=Flam|first=Faye|authorlink=Faye Flam|title=The Score: How the Quest for Sex Has Shaped the Modern Man|year=2008|publisher=Avery|page=88}}</ref> There is a range of external appearance that has been described of external genitalia at birth, with varying degrees of virilization.

===5α-Reductase 3===
When [[small interfering RNA]] is used to knock down the expression of 5α-R3 [[isozyme]] in [[cell lines]], there is decreased cell growth, viability, and a decrease in DHT/T ratios.<ref name="pmid17986282">{{cite journal |vauthors=Uemura M, Tamura K, Chung S, Honma S, Okuyama A, Nakamura Y, Nakagawa H | title = Novel 5 alpha-steroid reductase (SRD5A3, type-3) is overexpressed in hormone-refractory prostate cancer | journal = Cancer Sci. | volume = 99 | issue = 1 | pages = 81–6 |date=January 2008 | pmid = 17986282 | doi = 10.1111/j.1349-7006.2007.00656.x }}</ref> It has also shown the ability to reduce testosterone, androstenedione, and progesterone in androgen stimulated prostate cell lines by adenovirus vectors.<ref name="Azz"/>

Congenital deficiency of 5α-R3 at the gene SRD53A has been linked to a rare, autosomal recessive condition in which patients are born with severe intellectual dysfunction and cerebellar and ocular defects. The presumed deficiency is reduction of the terminal bond of polyprenol to dolichol, an important step in N-glycosylation of proteins, which in turn is important for proper folding of [[asparagine]] residues on nascent [[protein]] in the [[endoplasmic reticulum]].<ref name="pmid20637498">{{cite journal |vauthors=Cantagrel V, Lefeber DJ, Ng BG, Guan Z, Silhavy JL, Bielas SL, Lehle L, Hombauer H, Adamowicz M, Swiezewska E, De Brouwer AP, Blümel P, Sykut-Cegielska J, Houliston S, Swistun D, Ali BR, Dobyns WB, Babovic-Vuksanovic D, van Bokhoven H, Wevers RA, Raetz CR, Freeze HH, Morava E, Al-Gazali L, Gleeson JG | title = SRD5A3 is required for converting polyprenol to dolichol and is mutated in a congenital glycosylation disorder | journal = Cell | volume = 142 | issue = 2 | pages = 203–17 |date=July 2010 | pmid = 20637498 | pmc = 2940322 | doi = 10.1016/j.cell.2010.06.001 }}</ref>

==Nomenclature==
This enzyme belongs to the family of [[oxidoreductase]]s, to be specific, those acting on the CH-CH group of donor with other acceptors. The [[List of enzymes|systematic name]] of this enzyme class is '''3-oxo-5α-steroid:acceptor Δ<sup>4</sup>-oxidoreductase'''. Other names in common use include:

* 5α-Reductase
* 3-Oxosteroid Δ<sup>4</sup>-dehydrogenase
* 3-Oxo-5α-steroid Δ<sup>4</sup>-dehydrogenase
* Steroid Δ<sup>4</sup>-5α-reductase
* Δ<sup>4-3</sup>-Keto steroid 5α-reductase
* Δ<sup>4-3</sup>-Oxo steroid reductase
* Δ<sup>4-3</sup>-Ketosteroid-5α-oxidoreductase
* Δ<sup>4-3</sup>-Oxosteroid-5α-reductase
* 3-Keto-Δ<sup>4</sup>-steroid-5α-reductase
* Testosterone 5α-reductase
* 4-Ene-3-ketosteroid-5α-oxidoreductase
* Δ<sup>4</sup>-5α-Dehydrogenase
* 3-Oxo-5α-steroid:(acceptor) Δ<sup>4</sup>-oxidoreductase

==See also==
* [[Steroidogenic enzyme]]
* [[Acne vulgaris]]
* [[Cholestenone 5alpha-reductase|Cholestenone 5α-reductase]]
* [[Hirsutism]]
* [[Lower urinary tract symptoms]]
* [[Polycystic ovarian syndrome]]
* [[List of steroid metabolism modulators]]

==References==
{{Reflist|35em}}

==Further reading==
{{refbegin}}
* {{cite journal |vauthors=Levy HR, Talalay P | year = 1959 | title = Bacterial oxidation of steroids. II. Studies on the enzymatic mechanism of ring A dehydrogenation | journal = J. Biol. Chem.  | volume = 234 | pages = 2014&ndash;21  | pmid = 13673006 | issue = 8 }}
{{refend}}

==External links==
* {{MeshName|Testosterone+5-alpha-Reductase}}

{{Cholesterol and steroid metabolism enzymes}}
{{CH-CH oxidoreductases}}
{{Enzymes}}
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[[Category:EC 1.3.1]]