功能 |
Bifunctional enzyme with both ATP sulfurylase and APS kinase activity, which mediates two steps in the sulfate activation pathway. The first step is the transfer of a sulfate group to ATP to yield adenosine 5'-phosphosulfate (APS), and the second step is the transfer of a phosphate group from ATP to APS yielding 3'-phosphoadenylylsulfate (PAPS: activated sulfate donor used by sulfotransferase). In mammals, PAPS is the sole source of sulfate; APS appears to be only an intermediate in the sulfate- activation pathway. Also involved in the biosynthesis of sulfated L-selectin ligands in endothelial cells.
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總結(jié) |
Sulfotransferase (SULT) enzymes catalyze the sulfate conjugation of many drugs, xenobiotic compounds, hormones, and neurotransmitters. 3'-phosphoadenosine 5'-phosphosulfate (PAPS) synthase (PAPSS) catalyzes the biosynthesis of PAPS which serves as the universal sulfonate donor compound for all sulfotransferase reactions. In humans, PAPS is synthesized from adenosine 5-prime triphosphate (ATP) and inorganic sulfate by 2 isoforms, PAPSS1 and PAPSS2 (603005). Bifunctional PAPSS1 is comprised of an N-terminal APS kinase domain, and a C-terminal ATP sulfurylase domain. Full-length protein has significantly less APS kinase activity than the N-terminal fragment, suggesting that the C-terminal domain exerts a regulatory role on the N-terminal APS kinase activity. In humans there are two major isoforms: PAPSS1 and PAPSS2. In brain and skin PAPSS1 is the major isoform, whereas in liver, cartilage and adrenal glands PAPSS2 isoform expression dominates. The predicted 623-amino acid protein is 98% identical to mouse PAPS synthase. The N-terminal 268-amino acid region of human PAPS synthase resembles APS kinases from other organisms and contains 3 conserved nucleotide-binding motifs.
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