Multiple functions of type 10 17β-hydroxysteroid dehydrogenase

Human 17 beta-hydroxysteroid dehydrogenase type 10 (17 beta-HSD10) is a mitochondrial enzyme encoded by the SCHAD gene, which escapes chromosome X inactivation. 17 beta-HSD10/SCHAD mutations cause a spectrum of clinical conditions, from mild mental retardation to progressive infantile neurodegeneration. 17 beta-HSD10/SCHAD is essential for the metabolism of isoleucine and branched-chain fatty acids. It can inactivate 17 beta-estradiol and steroid modulators of GABA(A) receptors, and convert 5 alpha-androstanediol into 5 alpha-dihydrotestosterone (DHT). Certain malignant prostatic epithelial cells contain high levels of 17 beta-HSD10, generating 5 alpha-DHT in the absence of testosterone. 17 beta-HSD10 has an affinity for amyloid-beta peptide, and might be linked to the mitochondrial dysfunction seen in Alzheimer's disease. This versatile enzyme might provide a new drug target for neuronal excitability control and for intervention in Alzheimer's disease and certain cancers.