Adenylylsulfat

Adenylylsulfat, more commonly known as adenosine-5'-phosphosulfate (APS), is an activated form of sulfate used in sulfur metabolism in many microorganisms and plants. It is a nucleotide-like molecule comprising adenosine linked at the 5' position to a phosphate that carries a sulfate group.

APS is produced by the enzyme ATP sulfurylase, which catalyzes the reaction of sulfate with ATP to form APS and pyrophosphate. Once formed, APS can follow two main pathways. In assimilatory sulfate reduction, APS is reduced to sulfite by APS reductase, enabling incorporation of sulfur into biomolecules such as cysteine. Alternatively, APS can be phosphorylated by APS kinase to form 3'-phosphoadenosine-5'-phosphosulfate (PAPS), a universal sulfate donor in sulfotransferase reactions that transfer sulfate to a wide range of substrates, including proteins, carbohydrates, lipids, and xenobiotics.

APS and its downstream product PAPS play central roles in the sulfur assimilation and sulfation systems of many organisms. APS is especially important in plants and bacteria, where it participates in the synthesis of essential sulfur-containing compounds. In animals, APS is an intermediate in the activation of sulfate, while PAPS serves as the primary sulfate donor for sulfotransferase enzymes in various physiological processes. The term adenylylsulfat is used in some literature as a synonym for APS.