NTPDase1 and NTPDase2 are two related plasma mem-brane-located enzymes involved in the extracellular degra-dation of nucleoside 5¢-tri- and -diphosphates. They differ regarding their hydrolysis ratios for ATP and ADP. Both enzymes have a predicted transmembrane domain close to the N- and C-terminus, respectively, connected by an extensive extracellular domain that carries the active expressed the rat-derived enzymes inXenopus laevisoocytes and analyzed their quarternary structure.
