Sulfurylation of biomolecules (often termed sulfonation or sulfation) has been described in many organisms in all kingdoms of life. To date, most studies on
sulfotransferases, the
enzymes catalyzing sulfurylation, have focused on 3'-phosphate-5'-phosphosulfate (PAPS)-dependent
enzymes, which transfer the sulfuryl group from this activated
anhydride to
hydroxyl groups of acceptor molecules. By contrast, the PAPS-independent aryl
sulfotransferases (ASSTs) from bacteria, which catalyze sulfotransfer from phenolic
sulfate esters to another
phenol in the bacterial periplasm, were not well characterized until recently, although they were first described in 1986 in a search for nonhepatic sulfurylation processes. Recent studies revealed that this unusual class of
sulfotransferases differs profoundly in both molecular structure and catalytic mechanism from PAPS-dependent
sulfotransferases, and that ASSTs from certain bacterial pathogens are upregulated during
infection. In this review, we summarize the literature on the roles of sulfurylation in prokaryotes and analyze the occurrence of ASSTs and their dependence on
Dsb proteins catalyzing oxidative folding in the periplasm. Furthermore, we discuss structural differences and similarities between aryl
sulfotransferases and PAPS-dependent
sulfotransferases.