Mechanistic studies of β-arylsulfotransferase IV

Sulfotransferases are an important class of enzymes that catalyze the transfer of a sulfuryl group to a hydroxyl or amine moiety on various molecules including small-molecule drugs, steroids, hormones, carbohydrates, and proteins. They have been implicated in a number of disease states but remain poorly understood, complicating the design of specific, small-molecule inhibitors. A linear free-energy analysis in both the forward and reverse directions indicates that the transfer of a sulfuryl group to an aryl hydroxyl group catalyzed by beta-arylsulfotransferase IV likely proceeds by a dissociative (sulfotrioxide-like) mechanism. Values for the Bronsted coefficients (beta(nuc) and beta(Ig)) are + 0.33 and -0.45, giving Leffler alpha values of 0.19 and 0.61 for the forward and reverse reactions, respectively.