Journal article
Interactions of the stereoisomers of α-hydroxytamoxifen with human hydroxysteroid sulfotransferase SULT2A1 and rat hydroxysteroid sulfotransferase STA
Drug metabolism and disposition, Vol.32(12), pp.1501-1508
2004
DOI: 10.1124/dmd.104.000919
PMID: 15371299
Abstract
Tamoxifen (TAM) is a nonsteroidal antiestrogenic drug that is widely used for the treatment of estrogen receptor-dependent breast cancer. An increased risk of endometrial cancer in some patients treated with TAM has been linked to the metabolic formation of α-hydroxytamoxifen (α-OHTAM) and its subsequent sulfation. α-OHTAM has been found to be a substrate for rat and human hydroxysteroid sulfotransferases (STa and SULT2A1, respectively). Since stereochemistry plays an important role in the interactions of hydroxysteroid sulfotransferases with their substrates, we have now investigated the interactions of each of the stereoisomers of α-OHTAM with highly purified recombinant STa and SULT2A1. Methods for the preparation of the enantiomers of E- and Z-α-OHTAM were developed. When each of the four enantiomers was examined with rat STa, E-(+)-α-OHTAM was the only substrate for the enzyme, whereas E-(-)-α-OHTAM, Z-(+)-α-OHTAM, and Z-(-)-α-OHTAM were inhibitors of the sulfation of E-(+)-α-OHTAM catalyzed by STa. The dissociation constants for the α-OHTAM enantiomers indicated that they bound to STa with similar affinity, but only the E-(+)-enantiomer was a substrate. In contrast to the results obtained with rat hydroxysteroid sulfotransferase STa, all enantiomers of α-OHTAM were substrates for the human SULT2A1. Moreover, kcat/Km values with SULT2A1 were higher with the Z enantiomers than with the E enantiomers. As a result of the potential for interconversion of the E and Z geometric isomers upon metabolism, the sulfation of the Z isomers may be of greater concern in human tissues than has been previously assumed.
Details
- Title: Subtitle
- Interactions of the stereoisomers of α-hydroxytamoxifen with human hydroxysteroid sulfotransferase SULT2A1 and rat hydroxysteroid sulfotransferase STA
- Creators
- T IDIL APAK - Division of Medicinal and Natural Products Chemistry, College of Pharmacy, The University of Iowa, Iowa City, Iowa, United StatesMichael W Duffel - University of Iowa
- Resource Type
- Journal article
- Publication Details
- Drug metabolism and disposition, Vol.32(12), pp.1501-1508
- Publisher
- American Society for Pharmacology and Experimental Therapeutics
- DOI
- 10.1124/dmd.104.000919
- PMID
- 15371299
- ISSN
- 0090-9556
- eISSN
- 1521-009X
- Language
- English
- Date published
- 2004
- Academic Unit
- Molecular Physiology and Biophysics; Pharmaceutical Sciences and Experimental Therapeutics; Medicinal and Natural Products Chemistry
- Record Identifier
- 9984303285302771
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