adenosine5phosphosulfate

Adenosine-5'-phosphosulfate, often abbreviated as APS, is a crucial intermediate in biological sulfate assimilation. It is formed by the activation of inorganic sulfate. In most organisms, APS is synthesized from adenosine triphosphate (ATP) and sulfate by the enzyme ATP sulfurylase, producing APS and pyrophosphate. This molecule is a key donor of activated sulfate in various metabolic pathways. For instance, APS is a direct precursor to 3'-phosphoadenosine-5'-phosphosulfate (PAPS), the universal biological sulfate donor for sulfation reactions. PAPS is involved in the biosynthesis of glycosaminoglycans, sulfated steroids, and other important biomolecules. In some organisms, APS can also be directly utilized in sulfate reduction pathways, where it is further processed to sulfite, eventually leading to the formation of sulfide. The interconversion between APS and PAPS, along with their role in sulfate metabolism, highlights their central importance in cellular chemistry and the overall sulfur cycle.