Sulfurylase

Sulfurylase is an enzyme family that catalyzes the transfer of a sulfuryl group (SO3) from a donor to an acceptor substrate. In most contexts the primary activity is ATP sulfurylase, which catalyzes the activation of inorganic sulfate by converting it with ATP to adenosine 5'-phosphosulfate (APS) and pyrophosphate. This reaction is the first step in assimilatory sulfate metabolism in bacteria, algae, and plants, and supplies activated sulfate for biosynthetic pathways.

APS can be further phosphorylated by APS kinase to form 3'-phosphoadenosine-5'-phosphosulfate (PAPS), the universal sulfonyl donor used in sulfation reactions. Thus sulfurylase activity is a key entry point for sulfate into organic molecules such as glycosaminoglycans, glycoproteins, steroids, and xenobiotics via sulfation. In plants, bacteria, and some algae, ATP sulfurylase and APS kinase activities may be carried out by separate enzymes or by a bifunctional PAPS synthase.

Organisms vary in regulation; the enzyme generally requires Mg2+ and ATP; activity responds to sulfate availability. Structurally, ATP sulfurylases are often homodimers or mixed-domain enzymes with a catalytic sulfate-binding site and an ATP-binding site. The enzyme plays a central role in sulfur metabolism, environmental sulfur cycling, and biotechnological applications such as bioremediation and the production of sulfated biopolymers.

See also: ATP sulfurylase; APS kinase; PAPS; sulfation.