SRD5A3
steroid 5 alpha-reductase 3
Gene summary
A protein-coding gene on chromosome 4 (steroid hormone synthesis). The protein encoded by this gene belongs to the steroid 5-alpha reductase family, and polyprenol reductase subfamily. It is involved in the production of androgen 5-alpha-dihydrotestosterone (DHT) from testosterone, and maintenance of the androgen-androgen receptor activation pathway.
Source: NCBI Gene, accessed 2026-10-07.
Protein reference (UniProt)
- Protein
Polyprenal reductase
- Function
Plays a key role in early steps of protein N-linked glycosylation by being involved in the conversion of polyprenol into dolichol. Acts as a polyprenal reductase that mediates the reduction of polyprenal into dolichal in a NADP-dependent mechanism. Dolichols are required for the synthesis of dolichol-linked monosaccharides and the oligosaccharide precursor used for N-glycosylation. Also able to convert testosterone (T) into 5-alpha-dihydrotestosterone (DHT).
- Pathway
Protein modification; protein glycosylation.
- Subcellular location
Endoplasmic reticulum membrane.
- Tissue specificity
Expressed in preadipocytes (at protein level). Overexpressed in hormone-refractory prostate cancers (HRPC). Almost no or little expression in normal adult organs.
- Associated conditions
Congenital disorder of glycosylation 1Q (CDG1Q); Kahrizi syndrome (KHRZ).
Source: UniProtKB/Swiss-Prot Q9H8P0, release 2026_03, licensed CC BY 4.0. This is the protein’s normal biology, not evidence about post-drug syndromes; associated conditions are inherited disorders of the gene, not PFS, PSSD or PRSD.
Why its pathway is in the library
Steroid-synthesis enzymes sit directly on the pathways perturbed by 5-alpha-reductase inhibitors and SSRIs; inherited variation here is a candidate susceptibility factor for persistent post-drug phenotypes.
Written for the whole steroid synthesis family, not for SRD5A3 specifically.
Narrative library record
Function
Third 5-alpha-reductase isoenzyme (318 amino acids; about 20 percent homology with types 1 and 2); less characterized than types 1 and 2, with roles in protein N-glycosylation as well as steroid reduction.
Corpus relevance
Included in the PFS-011 systematic review of reductase biology; not a finasteride/dutasteride target of note, but completes the isoenzyme family for the corpus's pharmacology layer. Attribution: peer-reviewed (background pathway).
Mentioned in 5 corpus records
- Peer-reviewed paper
5α-Reductase Isoenzymes: From Neurosteroid Biosynthesis to Neuropsychiatric Outcomes
Rodríguez-Cerdeira, Carmen; Freus, Marika; Misiakiewicz-Has, Kamila; Pilutin, Anna; Kolasa, Agnieszka; Maksym, Radoslaw; Kajdy, Anna · NeuroSci (systematic review; PRISMA 2020)
PRISMA systematic review (PubMed/Scopus/Web of Science to Feb 2025; 83 included articles) on SRD5A1/2/3 tissue distribution: SRD5A1 drives CNS allopregnanolone synthesis; impaired neurosteroidogenesis from 5α-reductase inhibition is linked to anxiety…
SRD5A1SRD5A2SRD5A3PFS-0112025Core corpus - Peer-reviewed paper
Finasteride Concentrations and Prostate Cancer Risk: Results from the Prostate Cancer Prevention Trial
Cindy H. Chau, Douglas K. Price, Cathee Till, Phyllis J. Goodman, Xiaohong Chen, Robin J. Leach, Teresa L. Johnson-Pais, Ann Wu Hsing… · PLoS ONE
Using a nested case-control design inside the Prostate Cancer Prevention Trial, the authors measured serum finasteride by validated LC-MS and tested 27 SNPs in finasteride target and metabolism genes for association with drug concentrations. Five SNPs in…
CYP3A4CYP3A5SRD5A2SRD5A3MECH-0432015PFSSystems review · Oct 2026 - Glossary term
SRD5A3
enzyme
Gene encoding the third 5-alpha-reductase isoenzyme, less characterized than types 1 and 2 but included in the corpus's systematic review of reductase biology.
SRD5A3GL-srd5a3Core corpus - Gene record
3-oxo-5-alpha-steroid 4-dehydrogenase 1; converts testosterone to the more potent DHT and reduces progesterone, corticosterone, and other steroids via 5-alpha-reduction (hydride transfer from NADPH to carbon 5). Also active in bile-acid biosynthesis; broadly…
AKR1C2HSD3B1SRD5A1SRD5A2SRD5A3GENE-SRD5A1PFSCore corpus - Gene record
3-oxo-5-alpha-steroid 4-dehydrogenase 2; the dominant isoenzyme in prostate and genital skin, converting testosterone to DHT. Loss-of-function variants cause 5-alpha-reductase-2 deficiency, a 46,XY difference of sex development - direct human proof of what…
AKR1C2ARSRD5A1SRD5A2SRD5A3GENE-SRD5A2PFSCore corpus
Also in steroid hormone synthesis
All 38 genes- SRD5A2
steroid 5 alpha-reductase 2
chr 2· Steroid synthesis· 19 records - SRD5A1Powers
steroid 5 alpha-reductase 1
chr 5· Steroid synthesis· 17 records - AKR1C2Powers
aldo-keto reductase family 1 member C2
chr 10· Steroid synthesis· 12 records - AKR1C3Powers
aldo-keto reductase family 1 member C3
chr 10· Steroid synthesis· 9 records - CYP17A1
cytochrome P450 family 17 subfamily A member 1
chr 10· Steroid synthesis· 9 records - AKR1C4Powers
aldo-keto reductase family 1 member C4
chr 10· Steroid synthesis· 8 records - AKR1C1Powers
aldo-keto reductase family 1 member C1
chr 10· Steroid synthesis· 7 records - HSD3B2
hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 2
chr 1· Steroid synthesis· 7 records
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