Partial characterization of epididymal 5α reductase in the rat
Epididymal 5α reductase activity was found distributed in the crude nuclear fraction (44%) and microsomal fraction (41%). Spermatozoa contaminating the nuclear preparation accounted for only 3% of its activity. There were no regional differences in the distribution of total 5α reductase activity. Ho...
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| Autores principales: | , |
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| Formato: | JOUR |
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| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_0039128X_v30_n1_p41_Monsalve |
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| Sumario: | Epididymal 5α reductase activity was found distributed in the crude nuclear fraction (44%) and microsomal fraction (41%). Spermatozoa contaminating the nuclear preparation accounted for only 3% of its activity. There were no regional differences in the distribution of total 5α reductase activity. However, the nuclear enzyme was more active in caput than in other regions. Maximal activity was found at pH 6.2 and at 32°C. Both enzymes had an absolute requirement of reduced dinucleotides. The microsomal preparation could only use NADPH while the nuclear enzyme could use NADPH and NADH. The apparent Km for the microsomal preparation was 0.62 ± 0.05 × 10-6M and Vmax was 555 ± 38 pmoles/mg protein/hour. The nuclear enzyme presented similar values. The reaction was not inhibited by accumulation of product in the medium, but other steroids such as progesterone, epitestosterone(17α-hydroxy-4-androsten-3-one) and 3-oxo-4-androstene-17β-carboxylic acid were potent competitive inhibitors. The reaction was strongly inhibited by Hg, Zn and Cu. The properties of the epididymal reductase are similar to those of the prostatic enzyme. © 1977. |
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