May perform an important processing step in the conversion of high energy nucleotides prior to uptake by the parasite. NTPAse-II has a specific activity 4.5-fold lower than NTPAse-I in hydrolysis of ATP. The primary difference between these isozymes lies in their ability to hydrolyze nucleoside triphosphate versus diphosphate substrates. While NTPAse-II hydrolyzes ATP to ADP and ADP to AMP at almost the same rate, NTPAse-I hydrolyzes ADP to AMP at a much slower rate (0.7% of the rate for ATP). a ribonucleoside 5'-triphosphate + H2O = a ribonucleoside 5'-diphosphate + H(+) + phosphate Homotetramer. Found in host cell parasitophorous vacuole. Belongs to the GDA1/CD39 NTPase family.