adenylyltransferas

Adenylyltransferase, or adenylyltransferase, is a class of enzymes that catalyze the transfer of an adenylyl group (AMP) from ATP to a substrate. In this reaction, the substrate is activated by the addition of AMP, producing a substrate-AMP product and releasing pyrophosphate. These enzymes are broadly categorized within the nucleotidyltransferase superfamily and can act on a range of acceptors, including proteins, RNA, and small molecules.

A key characteristic of adenylyltransferases is their use of ATP as the AMP donor and their dependence on divalent cations such as Mg2+ or Mn2+ to facilitate catalysis. The exact mechanism and cellular role vary by enzyme and organism, but many adenylyltransferases form a transient adenylated intermediate on the substrate during catalysis.

Examples illustrate the diversity of substrate scope and biological function:

- Glutamine synthetase adenylyltransferase (GlnE) in bacteria catalyzes the reversible adenylylation and deadenylylation of glutamine synthetase, thereby regulating nitrogen metabolism in response to cellular cues.

- Poly(A) polymerase is an adenylyltransferase that adds adenine nucleotides from ATP to the 3' end of RNA, generating poly(A) tails that influence mRNA stability and translation in eukaryotes.

- Fic-domain proteins mediate AMP transfer to target proteins in a process known as AMPylation, a post-translational modification that can alter protein activity, interactions, or localization.

Distribution and significance: Adenylyltransferases are found across bacteria, archaea, and eukaryotes, reflecting their broad involvement in metabolism, RNA processing, and regulatory networks. The enzyme class encompasses both metabolic enzymes and modifying enzymes that control protein and RNA function.