PubMed · 55321
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K Shida, Z Ito, H Yamanaka. 1975. [Androgens].. https://pubmed.ncbi.nlm.nih.gov/55321/
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The 4-azasteroid 17 beta-(N-t-butyl)carbamoyl-4-aza-5 alpha-androst-1-en-3-one (finasteride) is 100-fold more potent as a competitive inhibitor of the rat NADPH:delta 4-3-oxosteroid-5-alpha- oxidoreductase (steroid 5 alpha-reductase) type 1 enzyme (Ki = 3-5 nM) than of the human type 1 enzyme (Ki greater than or equal to 300 nM). In this study, we exploit this differential sensitivity to map a major determinant of finasteride sensitivity in steroid 5 alpha-reductase. Chimeric steroid 5 alpha-reductase cDNAs composed of different combinations of rat and human exon sequences were created by genetic engineering, expressed in human embryonic kidney 293 cells, and assayed for their sensitivity to finasteride. Hybrid proteins containing sequences encoded by rat exon 1 were found to be as sensitive to finasteride as the parental enzyme. The exchange of progressively smaller protein segments encoded within exon 1 identified a tetrapeptide sequence (Val-Ser-Ile-Val) in the rat enzyme that conferred sensitivity to finasteride. The analogous sequence in the human enzyme (Ala-Val-Phe-Ala) conferred partial resistance to the drug. Finasteride was a competitive inhibitor of the native and all chimeric enzymes tested, suggesting that the tetrapeptide segments form a portion of the substrate-binding domain of steroid 5 alpha-reductase.
Analysis of the sexual determination and differentiation factors has progressed by the important findings made in biochemistry (hormonal assays, determination of the receptor concentration), in cellular and molecular endocrinology (mechanism of the hormonal action) and in genetics (identification, isolation and cloning of the genes implied in the sexual determination and differentiation pathways). We first describe the basis of sexual determination and differentiation, and then we analyze the different roles of SRY gene, encoding for the testis determining factor, androgen receptor gene, 5 alpha-reductase gene and anti-Müllerian hormone gene.
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