title: Structural and biochemical properties of cloned and expressed human and rat steroid 5 alpha-reductases.
abstract: The microsomal enzyme steroid 5 alpha-reductase is responsible for the conversion of testosterone into the more potent androgen dihydrotestosterone. In man, this steroid acts on a variety of androgen-responsive target tissues to mediate such diverse endocrine processes as male sexual differentiation in the fetus and prostatic growth in men. Here we describe the isolation, structure, and expression of a cDNA encoding the human steroid 5 alpha-reductase. A rat cDNA was used as a hybridization probe to screen a human prostate cDNA library. A 2.1-kilobase cDNA was identified and DNA sequence analysis indicated that the human steroid 5 alpha-reductase was a hydrophobic protein of 259 amino acids with a predicted molecular weight of 29,462. A comparison of the human and rat protein sequences revealed a 60% identity. Transfection of expression vectors containing the human and rat cDNAs into simian COS cells resulted in the synthesis of high levels of steroid 5 alpha-reductase enzyme activity. Both enzymes expressed in COS cells showed similar substrate specificities for naturally occurring steroid hormones. However, synthetic 4-azasteroids demonstrated marked differences in their abilities to inhibit the human and rat steroid 5 alpha-reductases.
authors.affiliation: Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas 75235.
authors.forename: S
authors.initials: S
authors.lastname: Andersson
authors.forename: D W
authors.initials: DW
authors.lastname: Russell
mesh_terms: D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D003001:Cloning, Molecular; D004247:DNA / Q000235:genetics; D015870:Gene Expression; D005822:Genetic Vectors; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D015345:Oligonucleotide Probes; D016133:Polymerase Chain Reaction; D051381:Rats; D012689:Sequence Homology, Nucleic Acid; D013379:Substrate Specificity; D014162:Transfection
chemical_list: D015345:Oligonucleotide Probes; D004247:DNA; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase