Blomquist Charles H.

No Thumbnail Available
Last Name
Blomquist
First Name
Charles H.
ORCID

Filters

2005 1
1
1
Reset filters

Settings
Author: Atkinson, M. J. ×

Search Results

Now showing 1 - 1 of 1
  • Preprint
    17β-Hydroxysteroid dehydrogenase (17β-HSD) in scleractinian corals and zooxanthellae
    ( 2005-12-18) Blomquist, Charles H. ; Lima, P. H. ; Tarrant, Ann M. ; Atkinson, M. J. ; Atkinson, S.
    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.