Molecular cloning, expression, and characterization of human bifunctional 3'-phosphoadenosine 5'-phosphosulfate synthase and its functional domains

J Biol Chem. 1998 Jul 24;273(30):19311-20. doi: 10.1074/jbc.273.30.19311.


The universal sulfonate donor, 3'-phosphoadenosine 5'-phosphosulfate (PAPS), is synthesized by the concerted action of ATP sulfurylase and adenosine 5'-phosphosulfate (APS) kinase, which in animals are fused into a bifunctional protein. The cDNA for human PAPS synthase (hPAPSS) along with polymerase chain reaction products corresponding to several NH2- and COOH-terminal fragments were cloned and expressed in COS-1 cells. A 1-268-amino acid fragment expressed APS kinase activity, whereas a 220-623 fragment evinced ATP sulfurylase activity. The 1-268 fragment and full-length hPAPSS (1-623) exhibited hyperbolic responses against APS substrate with equivalent Km values (0.6 and 0.4 microM, respectively). The 1-268 fragment demonstrated Michaelis-Menten kinetics against ATP as substrate (Km 0.26 mM); however, full-length hPAPSS exhibited a sigmoidal response (apparent Km 1.5 mM) suggesting cooperative binding. Catalytic efficiency (Vmax/Km) of the 1-268 fragment was 64-fold higher than full-length hPAPSS for ATP. The kinetic data suggest that the COOH-terminal domain of hPAPSS exerts a regulatory role over APS kinase activity located in the NH2-terminal domain of this bifunctional protein. In addition, the 1-268 fragment and full-length hPAPSS were overexpressed in Escherichia coli and column purified. Purified full-length hPAPSS, in contrast to the COS-1 cell-expressed cDNA construct, exhibited a hyperbolic response curve against ATP suggesting that hPAPSS is perhaps modified in vivo.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Binding Sites
  • COS Cells
  • Catalysis
  • Cloning, Molecular
  • Humans
  • Kinetics
  • Molecular Sequence Data
  • Multienzyme Complexes / genetics*
  • Multienzyme Complexes / metabolism
  • Sulfate Adenylyltransferase / genetics*
  • Sulfate Adenylyltransferase / metabolism


  • Multienzyme Complexes
  • PAPS synthetase
  • Sulfate Adenylyltransferase

Associated data

  • GENBANK/U53447