Diadenosine tetraphosphate or Ap4A is a putative alarmone, ubiquitous in nature being common to everything from bacteria to humans. Adenosine polyphosphates are capable of inducing multiple physiological effects. The molecule's role as a second messenger has recently been discovered in The LysRS-Ap4A-MITF signaling pathway. Myxococcus xanthus is a type of Gram-negative bacteria, and M. xanthus lysyl-tRNA synthetase (LysS) is an enzyme from the bacteria that synthesizes diadenosine tetraphosphates (Ap4A) when adenosine triphosphate (ATP) is present. Diadenosine pentaphosphate (Ap5A) is synthesized from Ap4A with ATP.