5-alpha reductase
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steroid-5-alpha-reductase, alpha polypeptide 1
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| Identifiers | |
| Symbol | SRD5A1 |
| HUGO | 11284 |
| Entrez | 6715 |
| OMIM | 184753 |
| RefSeq | NM_001047 |
| UniProt | P18405 |
| Other data | |
| EC number | 1.3.99.5 |
| Locus | Chr. 5 p15 |
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steroid-5-alpha-reductase, alpha polypeptide 2
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| Identifiers | |
| Symbol | SRD5A2 |
| HUGO | 11285 |
| Entrez | 6716 |
| OMIM | 607306 |
| RefSeq | NM_000348 |
| UniProt | P31213 |
| Other data | |
| EC number | 1.3.99.5 |
| Locus | Chr. 2 p23 |
5-alpha reductase is an enzyme that converts testosterone, the male sex hormone, into the more potent dihydrotestosterone:
Note the major difference -- the Δ4,5 double-bond on the A (leftmost) ring. (The other differences between the diagrams are unrelated to chemical structure.)
There are two isoenzymes, steroid 5-alpha reductase 1 and 2 (SRD5A1 and SRD5A2). The second isoenzyme is deficient in 5-alpha-reductase deficiency which leads to a form of intersexualism.
[edit] Production and inhibition
The enzyme is produced only in specific tissues of the male human body, namely the skin, seminal vesicles, prostate and epididymis.
Inhibition of 5-alpha reductase results in decreased production of DHT, increased levels of testosterone and possibly increased levels of estradiol. Gynecomastia is a possible side effect of 5-alpha reductase inhibition.
[edit] Pharmacology
5-alpha-reductase inhibitor drugs are used in benign prostatic hyperplasia, prostate cancer and baldness. Finasteride inhibits the function of only one of the isoenzymes (type 2), while dutasteride inhibits both forms.
[edit] External
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