Synonyms:ATPSK2 Background: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. May have a important role in skeletogenesis during postnatal growth(By similarity).