Reductase

A reductase is an enzyme that catalyzes a reduction reaction.

Examples

See also

References

SRD5A2

3-oxo-5-alpha-steroid 4-dehydrogenase 2 is an enzyme that in humans is encoded by the SRD5A2 gene.

Steroid 5-alpha reductase catalyzes the conversion of the male sex hormone testosterone into the more potent androgen, dihydrotestosterone.

This gene encodes a microsomal protein expressed at high levels in androgen-sensitive tissues such as the prostate. The encoded protein is active at acidic pH and is sensitive to the 4-azasteroid inhibitor finasteride. Deficiencies in this gene can result in male pseudohermaphroditism, specifically pseudovaginal perineoscrotal hypospadias (PPSH).

See also

References

Further reading

This article incorporates text from the United States National Library of Medicine, which is in the public domain.

5-alpha reductase

5α-reductases, also known as 3-oxo-5α-steroid 4-dehydrogenases, are enzymes involved in steroid metabolism. They participate in 3 metabolic pathways: bile acid biosynthesis, androgen and estrogen metabolism, and prostate cancer. There are three isoenzymes of 5-alpha reductase, which vary in different tissues with age.

5α-reductases catalyze the following chemical reaction:

Thus, the two substrates of these enzymes are a 3-oxo-5α-steroid and acceptor, whereas its two products are 3-oxo-Δ4-steroid and a reduced acceptor.

Production and activity

The enzyme is produced in many tissues in both males and females, in the reproductive tract, testes and ovaries,skin, seminal vesicles, prostate, epididymis and many organs, including the Nervous System. There are three isoenzymes of 5-alpha reductase: steroid 5α-reductase 1, 2, and 3 (SRD5A1, SRD5A2 and SRD5A3).

5α-reductases act on 3-oxo (3-keto), Δ4,5 C 19/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 4, 5'. The reaction involves a stereospecific and permanent break of the Δ 4, 5 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.