Ken-ichi Fujita, Kiyoshi Nagata (*), Eriko Watanabe, Miki Shimada and
Yasushi Yamazoe
Division of Drug Metabolism and Molecular Toxicology, Faculty of Pharmaceutical
Sciences, Tohoku University, Aramaki-Aoba, Aoba-ku, Sendai 980-8578, Japan
(*) To whom correspondence should be addressed.
Abstract: At least three forms of phenol sulfotransferase (ST)
ST1B1, ST1A1 and ST1C1 are contained in rat livers. To identify the form
contributing to the metabolism of 3,3',5-triiodothyronine (T3),
functional characterization of these forms was performed by expression in
Escherichia coli. ST1B1 and ST1C1 were shown to be active on sulfation towards
T3 with high affinity (Km: 44.4 and 25.8 microM, respectively),
whereas ST1A1 had low affinity. In Western blotting using antibodies raised
against the individual ST, hepatic contents of each ST were quantitatively
determined. ST1B1 showed no clear sex-difference, whereas the level of ST1C1
was higher in adult males than adult females. The content of ST1B1 was 1.4,
6.8 and 10 times higher than that of ST1C1 in adult males, adult females
and both sexes of immature rats, respectively. The developmental pattern
of ST1B1 was similar to that of ST1A1, but differed from that of ST1C1.
These results indicate that ST1B1 and ST1C1 are involved in T3
metabolism in rats and ST1B1 is the constitutive form across sexes and ages.
Keywords: Escherichia coli, Expression system, Histidine-tag, Phenol
sulfotransferase, Thyroid hormone