Specificity studies on bovine adrenal estrogen sulfotransferase.

The substrate requirements for estrogen sulfotransferase have been examined. Structural changes in all four rings of the estratriene nucleus affected sulfation. The V,,, of the reaction was increased from 1.4 to 3.2 times over that of estrone by nitro groups at positions 2 or 4, or the 6-keto function, while in the presence of a Z-amino group sulfation decreased to 1’ ,,3 and saturation of the A ring reduced sulfation to zero. The enzyme did not sulfate an OH in position 2 or 4 of estrogens but sulfated, with decreased efficiency, the phenolic-OH on 6-benzoyl-naphthol, anthraquinone, fluorenes, diphenyl, and tetraline. Examination of 60 structural variations has shown the optimal sulfation of the phenol&OH to require (a) the presence of a lipophilic side chain (7 A long, para to the OH), and (b) in the estratriene nucleus, an oxygen atom for hydrogen bonding to an area of the enzyme within 3.72 A above ring D.