Functional genome analysis indicates loss of 17beta-hydroxysteroid dehydrogenase type 2 enzyme in the zebrafish
- 关键词：Hydroxysteroid dehydrogenase ; Zebrafish ; Hsd17b2 ; Hsd11b2 ; Steroid ; Evolution ; Comparative endocrinology
- 刊名：The Journal of Steroid Biochemistry and Molecular Biology
- 出版年：2007
- 期刊代码：172_09600760
- 类别：med
- 出版时间：January 2007
- 卷：103
- 期：1
- 页码：35-43
- 文件大小：1066 K
摘要
Among the family of 17beta-hydroxysteroid dehydrogenases, the type 2 (17beta-HSD 2) is the main enzyme responsible for inactivation of estrogens and androgens, catalyzing the oxidation of the C17 hydroxyl group. 17beta-HSD 2 has been studied only in mammals, its occurrence and function in other vertebrates hardly known. We investigated the presence of homologs in non-mammalian species and found sequences of 17beta-HSD 2 and its closest homolog 11beta-HSD 2 in zebrafish (Danio rerio), Takifugu rubripes, Tetraodon nigroviridis, Xenopus tropicalis and chicken databases. Furthermore, we cloned zebrafish 17beta-HSD 2 from ovarian tissue and found high expression also in the testis of adult fish and throughout embryogenesis. The enzyme, though, is inactive likely due to a non-sense N-terminal region including a dysfunctional cofactor binding motif. Replacement of the affected part by the corresponding human 17beta-HSD 2 sequence fully restored enzymatic activity. Comparison of all retrieved 17beta-HSD 2 sequences indicates that this functional loss may have occurred only in zebrafish, where steroid inactivation at position C17 seems to pursue without the protein studied. The closely related 11beta-HSD 2 is unlikely to substitute for 17beta-HSD 2 since in our hands it did not catalyze the respective oxidation of testosterone or estradiol.