1. The dual sex hormone specificity for human reductive 17β-hydroxysteroid dehydrogenase type 7: Synergistic function in estrogen and androgen control.
- Author
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Thériault, Jean-François and Lin, Sheng-Xiang
- Subjects
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SEX hormones , *ESTROGEN , *BREAST cancer , *CANCER cells , *CELL proliferation , *LABORATORY mice - Abstract
Graphical abstract Highlights • 17β-HSD7 has similar steady-state kinetics parameters for activation of estrone and inactivation of DHT. • Substrate affinity of 17β-HSD7 toward estrone and DHT are similar. • Positive cooperativity of 17β-HSD7 for estrone and DHT in kinetic and affinity studies was obtained. • Successfully expressed and purified 17β-HSD7 in E.coli. Abstract Human 17β-hydroxysteroid dehydrogenase (17β-HSD) type 1 and 7 catalyze the final step of estrogen activation and the first step in androgen inactivation. It has been shown in breast cancer cells that DHT has a suppression effect on cell proliferation, counteracting the estrogen growth effect. However, the exact kinetic function of 17β-HSD7 in steroidogenesis was not determined. Here we report the steady-state kinetics and binding study for 17β-HSD7 with estrone or DHT as substrates and NADPH as cofactor. 17β-HSD7 has been overexpressed in E. coli and purified. For both substrates, kinetics of 17β-HSD7 demonstrates positive cooperativity. The K 0.5 value is 5.2 ± 0.4 μM and 14.4 ± 0.8 μM and the k cat is 0.0063 ± 0.0003 s−1 and 0.0153 ± 0.0007 s−1 for the reduction of E1 and DHT, respectively. The binding study shows a similar affinity with a dissociation constant of 5.2 ± 0.5 μM and 11 ± 1 μM for E1 and DHT, respectively. Our kinetic and binding results reveal a positive cooperativity for 17β-HSD7 to both the E1 and DHT with a similar affinity, while 17β-HSD1 demonstrated a significantly higher affinity toward E1 than DHT, but with a strong E1 substrate inhibition. These results strongly support that the inhibition of 17β-HSD7 constitutes the basis of breast cancer cell proliferation decreasing that led to the shrinkage of xenograft ER + breast tumor mice model. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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