17β-Hydroxysteroid dehydrogenase (17β-HSD) in scleractinian corals and zooxanthellae
Figure 2: 17β-HSD activity with E2 and T and the E2/T activity ratios for the samples of M. capitata and T. coccinea with the highest levels of activity with E2. (1.763Mb)
Figure 3: 17β-HSD activity with E2 and NADP+ or NAD+ as cofactor and the NADP+/NAD+ activity ratio for M. capitata homogenates and a sonicate of zooxanthellae. (3.020Mb)
Figure 4: 17β-HSD activity with E2 and NADP+ or NAD+ as cofactor and the NADP+/NAD+ activity ratios for T. coccinea homogenates with the highest levels of activity in two separate collections (#1, #2, #3 and #1A, #2A). (2.627Mb)
Figure 7: Time-course of E1 formation in zooxanthellae sonicate (squares) and M. capitata homogenate (circles) with NADP+ (filled symbols) or NAD+ (open symbols). (1.948Mb)
Figure 8: Effects of C18-hydroxysteroids, coumestrol and zearalanone on the conversion of E2 to E1 by M. capitata homogenate. (551.9Kb)
Figure 9: Effect of phytochemical inhibitors of mammalian 17β-HSDs on the conversion of E2 to E1 by M. capitata homogenate. (768.5Kb)
Blomquist, Charles H.
Lima, P. H.
Tarrant, Ann M.
Atkinson, M. J.
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Keyword17β-hydroxysteroid dehydrogenase; Steroid; Coral; Invertebrate; Zooxanthellae; Phytoestrogens; Estradiol; Scleractinia
Steroid metabolism studies have yielded evidence of 17β-hydroxysteroid dehydrogenase (17β-HSD) activity in corals. This project was undertaken to clarify whether there are multiple isoforms of 17β-HSD, whether activity levels vary seasonally, and if zooxanthellae contribute to activity. 17β-HSD activity was characterized in zooxanthellate and azooxanthellate coral fragments collected in summer and winter and in zooxanthellae cultured from M. capitata. More specifically, 17β-HSD activity was characterized with regard to steroid substrate and inhibitor specificity, coenzyme specificity, and Michaelis constants for estradiol (E2) and NADP+. Six samples each of M. capitata and T. coccinea (three summer, three winter) were assayed with E2 and NADP+. Specific activity levels (pmol/mg protein) varied 10-fold among M. capitata samples and 6-fold among T. coccinea samples. There was overlap of activity levels between summer and winter samples. NADP+/NAD+ activity ratios varied from 1.6 to 22.2 for M. capatita, 2.3 to 3.8 for T. coccinea and 0.7 to 1.1 for zooxanthellae. Coumestrol was the most inhibitory of the steroids and phytoestrogens tested. Our data confirm that corals and zooxanthellae contain 17β-HSD and are consistent with the presence of more than one isoform of the enzyme.
Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology 143 (2006): 397-403, doi:10.1016/j.cbpb.2005.12.017.
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