E - NTPDases ( Ecto - Nucleoside Triphosphate Diphosphohydrolase family , E - phosphohydrolase ATP) , previously called ecto- ATPases and ecto- apirazami , are enzymes which, in the presence of millimolar concentrations of extracellular divalent cations hydrolyze the tri- and diphosphonucleosides . Much evidence indicates that the E - NTPDases are involved in the transmission of information with ATP and P2 purynoreceptorów . The E phosphohydrolases ATP - neurotransmission is not limited to the removal of P2 receptor agonists .