Estrogen sulfotransferase activity in guinea pig uterus and chorion

Steroid Sulfotransferases

“…In contrast, gpEST expressed by CHO-K1 cells demonstrates MichaelisMenten kinetics (69), results similar to what has been reported for guinea pig uterus and chorion (72). The reason for the striking kinetic difference is not apparent.…”

“…EST purified from several tissues of a number of species is specific for the 3-hydroxyl or phenolic group of estrogenic steroids; it will not sulfonate either the 16a-or 17/3-hydroxyl group of phenolic steroids (67-69), nor will it sulfonate hydroxyl groups at positions 2 or 4 (70). Furthermore, EST will not sulfonate simple phenols (67,71,72). A notable feature of EST is its unusually high affinity for estrogen substrates.…”

“…For example, EST isolated from porcine endometrium has an apparent Michaelis-Menten constant (K m ) of 24 nM for estrone (73). Guinea pig EST (gpEST) isolated from the uterus and chorion has apparent K m values for estrone and 17j3-estradiol of approximately 100 nM (72). EST expressed by Chinese hamster ovary-Kl (CHO-K1) cells transfected with the guinea pig adrenal cDNA exhibits K m values of 60, 70, and 40 nM for estrone, 17j3-estradiol, and estriol, respectively (69).…”

Estrogen sulfotransferase of mouse placenta: behaviour and characteristics during partial purification

“…A variety of estrogen STs have been described in the reproductive and fetal tissues of some species Freeman et al 1983;Tseng et al 1985).…”

“…In these species a fetal factor may be involved in control of S T activity. These latter two enzymes have been partly purified and characterized in our laboratory Freeman et al 1983;Hobkirk et al 1985).…”