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, the activated sulfate donor used by sulfotransferases (PubMed:10559207). In mammals, PAPS is the sole source of sulfate while APS appears to only be an intermediate in the sulfate-activation pathway. May have an important role in skeletogenesis during postnatal growth. ATP + H(+) + sulfate = adenosine 5'-phosphosulfate + diphosphate adenosine 5'-phosphosulfate + ATP = 3'-phosphoadenylyl sulfate + ADP + H(+) Sulfur metabolism; sulfate assimilation. Expressed in liver, cartilage, skin and brain. Defects in Papss2 are the cause of brachymorphism (bm), a autosomal recessive disease, which is characterized by abnormal hepatic detoxification, bleeding times and postnatal growth, such as dome-shaped skull, short thick tail, and shortened but not widened limbs. The abnormal postnatal growth has been attributed to undersulfation of cartilage proteoglycans. In the N-terminal section; belongs to the APS kinase family. In the C-terminal section; belongs to the sulfate adenylyltransferase family.