Figure 1.

Nucleotidase activities of purified human PAP and recombinant human CD73. (a) The activities of hPAP and hCD73 were determined spectrophotometrically at neutral or acidic pH by using artificial substrate p-nitrophenylphosphate (pNPP). ND: nondetectable. Radio-TLC analysis of nucleotidase activities was also performed by incubating purified hPAP (b) and hCD73 (c) with 40 μM [³H]AMP at different pH without and with 5 μM AMPCP, as indicated. Enzymatic activities are expressed as μmoles of pNPP or [³H]AMP hydrolyzed per hour by one milligram of enzyme protein. *P < 0.05.