 In addition to the conserved lysine, sulfotransferases have a highly conserved histidine in the active site.Based on the conservation of these residues, theoretical models, and experimental measurements a theoretical transition state for catalyzed sulfation has been proposed (Figure 3).Carbohydrate sulfotransferases are transmembrane enzymes in the Golgi that modify carbohydrates on glycolipids or glyoproteins as they move along the secretory pathway.