Fig. 2.
Schematic outlining the aryl-sulfotransferase/O-sulfotransferase coupled assay. In a system initialized with PAPS, the O-sulfotransferase converts PAPS to PAP and sulfates the GAG. PAP is then recycled to PAPS by aryl-sulfotransferase with p-nitrophenylsulfate (R = NO2) acting as the sulfate donor. The products of the arylsulfotransferase reaction are PAPS, which is reused with the OST enzyme, and p-nitrophenol, PNP, which is measureable spectrophotometrically.