Purine-metabolizing enzymes in Babesia divergens

Extracts of Babesia divergens were examined for the enzymes which catalyse purine salvage. Adenosine deaminase (EC 3.5.4.4), guanine deaminase (EC 3.5.4.3), inosine phosphorylase (EC 2.4.2.1), purine phosphoribosyltransferases (EC 2.4.2.7, EC 2.4.2.8, EC 2.4.2.22) and nucleoside kinases (EC 2.7.1.15, EC 2.7.1.20, EC 2.7.1.73) were all detected at relatively high activities, whereas nucleotide interconverting enzymes were not detected. Coformycin and 4-amino-5-imidazolecarboxamide were found to be potent inhibitors of adenosine deaminase and guanine deaminase, respectively. The results suggest that B. divergens is capable of synthesizing purine nucleotides via two routes, one involving purine phosphoribosyltransferases and the other employing nucleoside kinases.