title: Regioselective monosulfation and disulfation of the phytoestrogens daidzein and genistein by human liver sulfotransferases.
abstract: Regioselective sulfation of the phytoestrogens daidzein (DZ, 7,4'-dihydroxyisoflavone) and genistein (GS, 5,7,4'-trihydroxyisoflavone) was investigated using human liver cytosol and purified recombinant human sulfotransferase (SULT) isoforms, SULT1A1, SULT1A3, SULT2A1, and SULT1E1. 7-Position-preferential sulfation of DZ and GS was observed in human hepatic cytosols from 3 male and 3 female subjects. Average ratios for 7- to 4'-sulfate formation were 4.5:1 from DZ and 8.4:1 from GS in these human liver cytosols. Apparent K(m) values for the 7- and 4'-sulfation of DZ and GS by these cytosols were similar and in a range from 0.46 to 0.66 microM. All recombinant human SULTs had activity for 7- and 4'-sulfation of these phytoestrogens except for 7-sulfating activity of SULT1A3. SULT1A1 and SULT1E1 exhibited much higher catalytic efficiency, k(cat)/K(m), for 7- and 4'-sulfation of these substrates than did the other two, SULT1A3 and SULT2A1. SULT1A1 showed K(m) values of 0.47 and 0.52 microM for the mono-sulfation of DZ and GS, respectively, which were very similar to those of human cytosol. The observed k(cat)/K(m) indicated that SULT1A1 catalyzed 7-sulfation of DZ and GS at rates 4.4- and 8.8-fold higher, respectively, than such 4'-sulfation. However, with SULT1E1, catalytic efficiency was very similar for the sulfation of both positions. These data strongly suggest that SULT1A1 plays a major role in monosulfation of the phytoestrogens and determines the regioselectivity of sulfation in human hepatic cytosol. A kinetic study for 7,4'-disulfate formation of DZ and GS from their 7- and 4'-monosulfates indicated that SULT1E1 most efficiently catalyzed both reactions among human SULTs.
authors.affiliation: Corporate, Scientific and Regulatory Affairs Division, Tobacco Headquarters, Japan Tobacco Inc., Tokyo.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakano
authors.forename: Kenichiro
authors.initials: K
authors.lastname: Ogura
authors.forename: Eriko
authors.initials: E
authors.lastname: Takahashi
authors.forename: Tomokazu
authors.initials: T
authors.lastname: Harada
authors.forename: Takahito
authors.initials: T
authors.lastname: Nishiyama
authors.forename: Kei
authors.initials: K
authors.lastname: Muro
authors.forename: Akira
authors.initials: A
authors.lastname: Hiratsuka
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Kadota
authors.forename: Tadashi
authors.initials: T
authors.lastname: Watabe
mesh_terms: D000328:Adult; D000368:Aged; D015239:Arylsulfotransferase / Q000378:metabolism; D005260:Female; D019833:Genistein / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007529:Isoflavones / Q000737:chemistry / Q000378:metabolism*; D008099:Liver / Q000201:enzymology*; D008297:Male; D008875:Middle Aged; D048789:Phytoestrogens / Q000737:chemistry / Q000378:metabolism*; D013237:Stereoisomerism; D013431:Sulfates / Q000378:metabolism; D015238:Sulfotransferases / Q000378:metabolism*
chemical_list: D007529:Isoflavones; D048789:Phytoestrogens; D013431:Sulfates; C004742:daidzein; D019833:Genistein; D015238:Sulfotransferases; D015239:Arylsulfotransferase; C117544:SULT1A1 protein, human; C403170:monoamine-sulfating phenol sulfotransferase; C028152:alcohol sulfotransferase; C020122:estrone sulfotransferase