20-amino and 20,21-aziridinyl pregnene steroids: development of potent inhibitors of 17 alpha-hydroxylase/C17,20-lyase (P450 17).
In the search for potent inhibitors of P450 17, the key enzyme of androgen biosynthesis, the 20,21-aziridinyl- and 20-aminopregnene steroids 1-11 were synthesized and tested toward rat testicular P450 17. Only the aziridinyl-substituted pregnenolones (1 and 2) and progesterones (3 and 4), respectively, showed inhibitory activity, which strongly depends on C20 stereochemistry. The most active compound 1 [20(S)-20,21-aziridinylpregn-5-en-3 beta-ol; IC50 0.21 microM, progesterone 25 microM; Ki = 1.7 nM, K(m) progesterone = 7.0 microM] is the strongest inhibitor of rat P450 17 described so far. Using UV-vis difference spectroscopy, complexation of the aziridinyl nitrogen to the heme iron, Fe3+, of P450 17 was observed, which could not be reversed by high concentrations of substrate. Preincubation of the enzyme with 1 in the absence and presence of NADPH followed by charcoal treatment results in a strong decrease of enzyme activity within 30 s. However, a recovery of enzyme activity was observed: 90 min after charcoal treatment 75% of the activity was restored.
Fachrichtung 12.1 Pharmazeutische Chemie, Universität des Saarlandes, Saarbrücken, Germany.
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D000818:Animals; D001388:Aziridines; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors / Q000737:chemistry* / Q000494:pharmacology; D008297:Male; D011283:Pregnenes / Q000737:chemistry* / Q000494:pharmacology; D051381:Rats; D013254:Steroid 17-alpha-Hydroxylase / Q000037:antagonists & inhibitors*; D013737:Testis / Q000201:enzymology
D001388:Aziridines; D065607:Cytochrome P-450 Enzyme Inhibitors; D004791:Enzyme Inhibitors; D011283:Pregnenes; D013254:Steroid 17-alpha-Hydroxylase