ATPsulfurylas

ATP sulfurylase (also ATP-sulfurylase or sulfate adenylyltransferase) is an enzyme that catalyzes the reversible activation of inorganic sulfate by transfer of an adenylyl group from ATP to form adenosine 5'-phosphosulfate (APS) and pyrophosphate (PPi). The overall reaction is typically written as: ATP + SO4(2-) ⇌ APS + PPi. This activation step is the gateway to biological sulfur metabolism.

ATP sulfurylase is found across bacteria, archaea, fungi, plants and algae, and participates in both assimilatory and dissimilatory sulfate pathways. In assimilatory metabolism, APS can be further converted to 3'-phosphoadenosine 5'-phosphosulfate (PAPS) or reduced to sulfite and then incorporated into amino acids such as cysteine and methionine. In dissimilatory sulfate reduction, APS is reduced as part of energy-yielding pathways in sulfate-reducing microorganisms.

The enzyme can occur as a single polypeptide or as multi-subunit complexes depending on the organism, and it commonly requires divalent metal ions (for example Mg2+) for activity. Structural studies show conserved nucleotidyltransferase motifs and diverse oligomeric assemblies. Expression and activity of ATP sulfurylase are regulated according to sulfur availability and metabolic demand. Because it catalyzes the committed step in sulfate activation, ATP sulfurylase is central to sulfur homeostasis and has been a subject of biochemical and evolutionary studies.