PAPSS1, also known as bifunctional 3'-phosphoadenosine 5'-phosphosulfate synthase 1, is a bifunctional enzyme with both ATP sulfurylase and APS kinase activity, which mediates two steps in the sulfate activation pathway, yielding 3'-phosphoadenylylsulfate (PAPS). PAPSS1 is also involved in the biosynthesis of sulfated L-selectin ligands in endothelial cells. Recombinant human PAPSS1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography.