Tc. Ganguly et al., BACTERIAL EXPRESSION AND KINETIC CHARACTERIZATION OF THE HUMAN MONOAMINE-SULFATING FORM OF PHENOL SULFOTRANSFERASE, Drug metabolism and disposition, 23(9), 1995, pp. 945-950
The cDNA for the human monoamine-sulfating form of phenol sulfotransfe
rase (hM-PST) was isolated from a T47D human breast carcinoma lambda g
t10 cDNA library, and the active enzyme was expressed in Escherichia c
oli, Expressed hM-PST was very similar to the brain, intestinal, and p
latelet forms of the enzyme in its physical, immunological, and kineti
c properties. The ability of hM-PST to sulfate a number of xenobiotics
was examined and compared with the bacterially expressed human phenol
-sulfating form of PST (hP-PST), The translation product of the T47D h
M-PST cDNA was 92% identical to that of liver hP-PST. Monoamine neurot
ransmittors, such as epinephrine and dopamine, were maximally conjugat
ed at lower concentrations by expressed hM-PST (2 and 20 mu M, respect
ively) than by hP-PST (1 and 1 mM, respectively). In contrast, simple
phenols-such as p-nitrophenol, acetaminophen, and alpha-naphthol-were
maximally conjugated at lower concentrations(4 mu M, 20 mu M, and 0.5
mu M, respectively) by hP-PST than by hM-PST (1 mM, 1.5 mM, and 50 mu
M, respectively). Minoxidil was sulfated at similar rates and concentr
ations (7 mM) by both forms of PST. None of the estrogens or related c
ompounds, such as beta-estradiol, 17 alpha-ethinylestradiol, diethylst
ilbestrol, equilenin, or genistein tested as substrates were sulfated
by hM-PST; however, all of these compounds were substrates for hP-PST,
As with hP-PST, the hydroxysteroids dehydroepiandrosterone and cortis
ol were not sulfated by hM-PST. In addition, inhibition studies sugges
t that the amino acid differences between hM-PST and hP-PST are of ade
quate significance to prevent compounds with a sterol-like structure f
rom binding the active site of hM-PST, These results indicate that the
re are important differences in the substrate reactivities of the two
PSTs and that expression of the individual human STs in bacteria is a
valuable tool for the investigation of differences in drug and xenobio
tic metabolism.