PYRIMIDINE NUCLEOTIDASES FROM HUMAN ERYTHROCYTE POSSESS PHOSPHOTRANSFERASE ACTIVITIES SPECIFIC FOR PYRIMIDINE NUCLEOTIDES

Two cytoplasmic forms of pyrimidine nucleotidase (PN-I and PN-II) have been purified from human erythrocytes to apparent homogeneity and par tially characterized. They preferentially hydrolyse pyrimidine 5'-mono phosphates and 3'-monophosphates respectively. PN-I and PN-II operate as interconverting activities, capable of transferring the phosphate f rom the pyrimidine nucleoside monophosphate donor(s) to various nucleo side accepters, including important drugs like 3'-azido-3'-deoxy-thymi dine (AZT), cytosine-beta-D-arabinofuranoside (AraC) and 5-fluoro-2'-d eoxy-uridine (5FdUrd), pyrimidine analogues widely used in chemotherap y. Kinetic analysis showed linear behaviour for both PN-I and PN-II. P N-I phosphotransferase activity revealed higher affinity for oxynucleo sides with respect to deoxy-nucleosides, whereas the contrary seems to be true for PN-II. These results show for the first time that soluble pyrimidine nucleotidases are endowed with pyrimidine-specific phospho transferase activity. (C) 1997 Federation of European Biochemical Soci eties.