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Mouse steroid sulfotransferases: substrate specificity and preliminary X-ray crystallographic analysis
Y Kakuta1, L C Pedersen, K Chae
1Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, NC 27709, USA.
Biochemical Pharmacology
|March 4, 1998
Summary
Mouse sulfotransferases show specific activity towards natural steroid hormones but efficiently metabolize synthetic estrogen, diethylstilbestrol. These enzymes exhibit stereospecificity, acting only on the trans-isomer of diethylstilbestrol.
Area of Science:
- Biochemistry
- Enzymology
- Structural Biology
Background:
- Cytosolic sulfotransferases (SULTs) play crucial roles in the metabolism of endogenous and exogenous compounds, including steroid hormones.
- Understanding SULT substrate specificity is vital for drug development and comprehending hormone signaling pathways.
Purpose of the Study:
- To investigate the substrate specificities of three mouse cytosolic sulfotransferases towards natural and synthetic steroid hormones.
- To characterize the kinetic parameters (Km and Vmax) and stereospecificity of these enzymes.
- To obtain high-resolution structural data of estrogen sulfotransferase.
Main Methods:
- Recombinant expression of three mouse cytosolic sulfotransferases in Escherichia coli.
- Enzymatic assays using natural (estradiol, dehydroepiandrosterone) and synthetic (diethylstilbestrol) steroid hormones.
- Kinetic analysis to determine Km and Vmax values.
- Crystallization of estrogen sulfotransferase and X-ray diffraction analysis.
Main Results:
- Estrogen and hydroxysteroid sulfotransferases demonstrated high substrate specificity for estradiol and dehydroepiandrosterone, respectively.
- Both enzymes efficiently metabolized the synthetic estrogen diethylstilbestrol to its disulfate ester.
- The sulfotransferases exhibited stereospecificity, exclusively sulfating the trans-isomer of diethylstilbestrol.
- Crystals of estrogen sulfotransferase were obtained, belonging to the P2(1)2(1)2 space group and diffracting to 2.5 A resolution.
Conclusions:
- Mouse cytosolic sulfotransferases possess distinct substrate specificities for natural steroid hormones but can efficiently process synthetic estrogens like diethylstilbestrol.
- The observed stereospecificity in diethylstilbestrol metabolism highlights the precise molecular recognition capabilities of these enzymes.
- The structural data of estrogen sulfotransferase will facilitate a deeper understanding of enzyme-substrate interactions and mechanism of action.