MOLECULAR CHARACTERIZATION OF A TESTIS-SPECIFIC ESTROGEN SULFOTRANSFERASE AND ABERRANT LIVER EXPRESSION IN OBESE AND DIABETOGENIC C57BL KSJ-DB/DB MICE/

Sulfation represents a major pathway for the inactivation of steroid h ormones such as estrogens and is catalyzed by a group of enzymes calle d sulfotransferases. Aberrant regulation of an estrogen sulfotransfera se has been demonstrated previously in the livers of obese and diabeto genic C57BL/KsJ-db/db strain mice. In this paper, we report the molecu lar cloning and functional characterization of a full-length complemen tary DNA for estrogen sulfotransferase from mouse testis. The mouse es trogen sulfotransferase complementary DNA encodes 295 amino acids. It shares 88%, 77%, 75%, and 68% identity in amino acid sequence with the rat liver, human liver, guinea pig adrenal, and bovine placental estr ogen sulfotransferase, respectively. The mouse enzyme was expressed as a glutathione-S-transferase fusion protein in Escherichia coli. The f usion protein was affinity purified, and milligram quantities of pure enzyme were obtained after cleavage of the fusion protein with thrombi n. The expressed enzyme exhibits a high substrate specificity toward e strogens, including estradiol and estrone. Neither dehydroepiandroster one, pregnenolone, testosterone, nor a simple phenolic compound, 4-nit rophenol appears to be a substrate. Northern hybridization indicates t hat messenger RNA (1.3 kilobases) for the estrogen sulfotransferase is expressed exclusively in the testes in control G57BL/KsJ mice. Howeve r, both the messenger RNA and protein are dramatically induced in the livers of obese and diabetogenic C57BL/KsJ-db/db mice. In contrast to the liver, the constitutive expression of the enzyme in the testis is not affected by the db/db genotype. These results recapitulate the spe cies-specific nature in the tissue distribution of estrogen sulfotrans ferase and suggest complex regulatory mechanisms in its expression und er normal and pathophysiological conditions.