Reaction product affinity regulates activation of human sulfotransferase 1A1 PAP sulfation.
Cytosolic sulfotransferase (SULT)-catalyzed sulfation regulates the activity of bio-signaling molecules and aids in metabolizing hydroxyl-containing xenobiotics. The sulfuryl donor for the SULT reaction is adenosine 3'-phosphate 5'-phosphosulfate (PAPS), while products are adenosine 3',5'-diphosphate (PAP) and a sulfated alcohol. Human phenol sulfotransferase (SULT1A1) is one of the major detoxifying enzymes for phenolic xenobiotics. The mechanism of SULT1A1-catalyzed sulfation of PAP by pNPS was investigated. PAP was sulfated by para-nitrophenyl sulfate (pNPS) in a concentration-dependent manner. 2-Naphthol inhibited sulfation of PAP, competing with pNPS, while phenol activated the sulfation reaction. At saturating PAP, a ping pong kinetic mechanism is observed with pNPS and phenol as substrates, consistent with phenol intercepting the E-PAPS complex prior to dissociation of PAPS. At high concentrations, phenol competes with pNPS, consistent with formation of the E-PAP-phenol dead-end complex. Data are consistent with the previously reported mechanism for sulfation of 2-naphthol by PAPS, and its activation by pNPS. Overall, data are consistent with release of PAP from E-PAP and PAPS from E-PAPS contributing to rate-limitation in both reaction directions.
Department of Physiological Sciences, Center for Veterinary Health Sciences, Oklahoma State University, Stillwater, OK 74078, USA.
Eduard
E
Tyapochkin
Vidya Prasanna
VP
Kumar
Paul F
PF
Cook
Guangping
G
Chen
D000244:Adenosine Diphosphate / Q000378:metabolism; D015239:Arylsulfotransferase / Q000037:antagonists & inhibitors / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007700:Kinetics; D008954:Models, Biological; D009284:Naphthols / Q000494:pharmacology; D009578:Nitrobenzenes / Q000378:metabolism; D019800:Phenol / Q000494:pharmacology; D010724:Phosphoadenosine Phosphosulfate / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000037:antagonists & inhibitors / Q000737:chemistry / Q000378:metabolism; D013379:Substrate Specificity
D004791:Enzyme Inhibitors; D009284:Naphthols; D009578:Nitrobenzenes; D011993:Recombinant Fusion Proteins; C023379:4-nitrophenyl sulfate; D019800:Phenol; D010724:Phosphoadenosine Phosphosulfate; D000244:Adenosine Diphosphate; C010840:adenosine 3'-phosphate-5'-phosphate; D015239:Arylsulfotransferase; C117544:SULT1A1 protein, human; C028405:2-naphthol