PAPs

PAPS stands for 3'-phosphoadenosine-5'-phosphosulfate, a nucleotide-sugar that serves as the principal high-energy sulfate donor in sulfation reactions across many organisms. In cells, PAPS is produced in the cytosol and Golgi apparatus by PAPS synthase enzymes, specifically PAPSS1 and PAPSS2, from ATP and inorganic sulfate via an APS intermediate.

Biosynthesis of PAPS involves two catalytic steps within PAPSS enzymes. First, ATP sulfurylase activity converts sulfate and ATP to adenosine 5'-phosphosulfate (APS). Then APS kinase activity converts APS to PAPS. The two activities are integrated in a single enzyme complex, allowing efficient channeling of the sulfate donor to sulfation reactions.

Functionally, sulfotransferases transfer the sulfate group from PAPS to a wide range of substrates, including hormones, neurotransmitters, xenobiotics, and carbohydrates such as glycosaminoglycans. After the transfer, the byproduct 3'-phosphoadenosine-5'-phosphate (PAP) is typically recycled by PAP phosphatases, such as BPNT1, which hydrolyze PAP to AMP and phosphate, providing a salvage pathway that maintains sulfate homeostasis.

Clinical relevance includes the observation that mutations in PAPSS2 can cause skeletal dysplasias due to disrupted sulfation of cartilage proteoglycans. Altered PAPS synthesis and sulfation patterns have also been linked to osteoarthritis and other developmental or metabolic conditions, reflecting the broad role of sulfation in physiology.

Other uses: In different contexts, PAPS can be an acronym for terms such as Public Assistance Programs or Pre-Authorized Payment Systems, depending on jurisdiction and field. These usages are unrelated to the biochemical molecule described above.