Facilitates hematophagy by inhibiting ADP-dependent platelet aggregation in the host. May reduce probing time by facilitating the speed of locating blood. Platelet aggregation was inhibited by 6% when 0.4 uM recombinant apyrase was added and by 9.5% when the concentration of recombinant apyrase was 0.8 uM. a ribonucleoside 5'-triphosphate + 2 H2O = a ribonucleoside 5'-phosphate + 2 H(+) + 2 phosphate Salivary gland specific. Causes an allergic reaction in human. Belongs to the 5'-nucleotidase family.