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{{enzyme
| Name = 3β-hydroxy-5α-steroid dehydrogenase
| EC_number = 1.1.1.278
| CAS_number = 9015-81-0
| IUBMB_EC_number = 1/1/1/278
| GO_code = 0033704
| image = 
| width = 
| caption = 
}}
In [[enzymology]], a '''3β-hydroxy-5α-steroid dehydrogenase''' ({{EC number|1.1.1.278}}) is an [[enzyme]] that [[catalysis|catalyzes]] the [[chemical reaction]]

:3β-hydroxy-5α-pregnane-20-one + NADP<sup>+</sup> <math>\rightleftharpoons</math> 5α-pregnan-3,20-dione + NADPH + H<sup>+</sup>

Thus, the two [[substrate (biochemistry)|substrates]] of this enzyme are [[allopregnanolone|3β-hydroxy-5α-pregnane-20-one]] (allopregnanolone) and [[nicotinamide adenine dinucleotide phosphate|NADP<sup>+</sup>]], whereas its 3 [[product (chemistry)|products]] are [[5α-pregnan-3,20-dione]], [[nicotinamide adenine dinucleotide phosphate|NADPH]], and [[hydrogen ion|H<sup>+</sup>]].

This enzyme belongs to the family of [[oxidoreductase]]s, specifically those acting on the CH-OH group of donor with NAD<sup>+</sup> or NADP<sup>+</sup> as acceptor. The systematic name of this enzyme class is '''3β-hydroxy-5α-steroid:NADP<sup>+</sup> 3-oxidoreductase'''.

==References==
{{reflist|1}}
{{refbegin}}
* {{cite journal | author = Lindemann P and Luckner M | date = 1997 | title = Biosynthesis of pregnane derivatives in somatic embryos of ''Digitalis lanata'' | journal = [[Phytochemistry (journal)|Phytochemistry]] | volume = 46 | pages = 507&ndash;513 | doi = 10.1016/S0031-9422(97)00315-4 | issue = 3 }}
* {{cite journal | author = Warneck HM, Seitz HU | date = 1990 | title = 3 beta-hydroxysteroid oxidoreductase in suspension cultures of ''Digitalis lanata'' EHRH | journal = Z. Naturforsch. [C]. | volume = 45 | pages = 963&ndash;72 | pmid = 2291772 | issue = 9–10 }}
{{refend}}
[[Category:EC 1.1.1]]
[[Category:NADPH-dependent enzymes]]
[[Category:Enzymes of unknown structure]]

{{1.1.1-enzyme-stub}}