Abstract
17β-Hydroxysteroid dehydrogenase type 1 (17β-HSD1) catalyzes the conversion of estrone to the potent estrogen estradiol. 17β-HSD1 is highly expressed in breast and ovary tissues and represents a prognostic marker for the tumor progression and survival of patients with breast cancer and other estrogen-dependent tumors. Therefore, the enzyme is considered a promising drug target against estrogen-dependent cancers. For the development of novel inhibitors, an improved understanding of the structure-function relationships is essential. In the present study, we examined the role of a cysteine residue, Cys10, in the Rossmann-fold NADPH binding region, for 17β-HSD1 function and tested the sensitivity towards sulfhydryl modifying chemicals. 3D structure modeling revealed important interactions of Cys10 with residues involved in the stabilization of amino acids of the NADPH binding pocket. Analysis of enzyme activity revealed that 17β-HSD1 was irreversibly inhibited by the sulfhydryl modifying agents N-ethylmaleimide (NEM) and dithiocarbamates. Preincubation with increasing concentrations of NADPH protected 17β-HSD1 from inhibition by these chemicals. Cys10Ser mutant 17β-HSD1 was partially protected from inhibition by NEM and dithiocarbamates, emphasizing the importance of Cys10 in the cofactor binding region. Substitution of Cys10 with serine resulted in a decreased protein half-life, without significantly altering kinetic properties. Despite the fact that Cys10 on 17β-HSD1 seems to have limited potential as a target for new enzyme inhibitors, the present study provides new insight into the structure-function relationships of this enzyme.
Highlights
17β-Hydroxysteroid dehydrogenase (17β-HSD) enzymes are involved in the interconversion of inactive and active sex-steroid hormones, thereby playing an essential role in the intracrine regulation of estrogen, androgen, and progesterone-dependent physiological functions [1]. 17βHSD1 is responsible for the conversion of estrone to estradiol, the most potent natural estrogen
We examined the role of a cysteine residue, Cys10, in the Rossmann-fold NADPH binding region, for 17β-HSD1 function and tested the sensitivity towards sulfhydryl modifying chemicals. 3D structure modeling revealed important interactions of Cys10 with residues involved in the stabilization of amino acids of the NADPH binding pocket
The cysteine and the two downstream serine residues are present in all-trans retinol dehydrogenase RDH8, which like 17β-HSD1 belongs to the SDR28C family
Summary
17β-Hydroxysteroid dehydrogenase (17β-HSD) enzymes are involved in the interconversion of inactive and active sex-steroid hormones, thereby playing an essential role in the intracrine regulation of estrogen-, androgen-, and progesterone-dependent physiological functions [1]. 17βHSD1 is responsible for the conversion of estrone to estradiol, the most potent natural estrogen. 17β-Hydroxysteroid dehydrogenase (17β-HSD) enzymes are involved in the interconversion of inactive and active sex-steroid hormones, thereby playing an essential role in the intracrine regulation of estrogen-, androgen-, and progesterone-dependent physiological functions [1]. The administration of specific 17β-HSD1 inhibitors led to significantly decreased tumor growth in breast cancer cell xenograft tumor mouse models [7, 8] and reversed estrogendependent endometrial hyperplasia in transgenic mice [9], indicating that this enzyme is a promising drug target against estrogen-dependent diseases such as endometriosis and endometrial cancer as well as breast and ovarian tumors. We demonstrated that the structurally related enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) contains a cysteine residue at position 90, analogous to Cys on 17β-HSD1 [20]. We applied 3D structure modeling and enzyme activity measurements to investigate the biochemical properties of Cys10Ser mutant 17β-HSD1 and to compare its sensitivity towards sulfhydryl modifying agents with that of wild-type 17β-HSD1
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
