Flavonoid inhibition of overexpressed human 3beta-hydroxysteroid dehydrogenase type II.
The inhibitory effects of various flavonoids on human 3beta-hydroxysteroid dehydrogenase/Delta(5)-Delta(4)-isomerase type II (3beta-HSD type II), overexpressed in baculovirus, were investigated, and the structure-inhibition relationship was examined. The isoflavone derivatives daidzein, genistein, formononetin and biochanin A inhibited 3beta-HSD type II activity at a concentration of 10 microM and of these, genistein was the most potent inhibitor. 6-Hydroxyflavone (6-HF), a synthetic flavone, also strongly inhibited 3beta-HSD activity but 5-HF, 7-HF and other natural flavones were less potent. Energy minimization structures of the flavonoids, as produced using MOE software, showed that isoflavones and flavones have an almost flat A-C ring structure, and that flavonoids that acted as inhibitors had similar steric structures to DHEA. Genistein, 6-HF and cyanoketone, which is known as a typical 3beta-HSD inhibitor, were found to act as competitive inhibitors with K(i) values of 0.12 microM, 0.19 microM and 0.67 nM, respectively. Furthermore, the LUMO (lowest unoccupied molecular orbital (LUMO)) values, as calculated using WinMOPAC (Fujitsu, Japan), of the inhibitors were correlated with the IC(50) values (r2 = 0.84). From these results, it appears that inhibitory effects of flavonoids are due to the combination of steric structure and electron affinity between the active center of 3beta-HSD type II and the flavonoid molecule.
Ohno
Shuji
S
Department of Biochemistry, Hoshi University School of Pharmacy and Pharmaceutical Sciences, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan. ohno@hoshi.ac.jp
Matsumoto
Noriko
N
Watanabe
Masatada
M
Nakajin
Shizuo
S
D015096:3-Hydroxysteroid Dehydrogenases / Q000037:antagonists & inhibitors*; D000818:Animals; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005419:Flavonoids / Q000494:pharmacology*; D006801:Humans; D007700:Kinetics; D011994:Recombinant Proteins / Q000037:antagonists & inhibitors; D018411:Spodoptera; D013329:Structure-Activity Relationship; D013347:Subcellular Fractions / Q000201:enzymology
D017931:DNA Primers; D004791:Enzyme Inhibitors; D005419:Flavonoids; D011994:Recombinant Proteins; D015096:3-Hydroxysteroid Dehydrogenases