Adenosine 5â²-tetraphosphate, Ap4 or ATPP is a nucleotide. It is produced from ATP and triphosphate (P<sub>3</sub>) through the action of acetylâÂÂCoA synthetase. AcetylâÂÂCoA synthetase also produces adenosine 5'-pentaphosphate through the reaction of ADP and tetraphosphate (P<sub>4</sub>).
ATPP has been found to play physiological roles in some mammals.
ATPP is a constituent of aqueous humor in rabbits, where it was found to reduce the intraocular pressure.
ATPP has been suggested to play a regulatory role in rat aorta.