INVITRO BIOLOGICAL-ACTIVITY OF 9-BETA-D-ARABINOFURANOSYL-2-FLUOROADENINE AND THE BIOCHEMICAL ACTIONS OF ITS TRIPHOSPHATE ON DNA-POLYMERASES AND RIBONUCLEOTIDE REDUCTASE FROM HELA-CELLS

  • 1 January 1982
    • journal article
    • research article
    • Vol. 21  (2) , 474-477
Abstract
9-.beta.-D-Arabinofuranosyl-2-fluoroadenine (2-F-araA) inhibited the growth in vitro of HeLa (human cervical carcinoma) cells by 50% at a concentration of 0.25 .mu.M and depressed the replication of herpes simplex virus types 1 and 2 by 99% at 25 .mu.M. The analog served as a substrate for cytoplasmic but not mitochondrial deoxycytidine (dCyd) kinase partially purified from human peripheral chronic lymphocytic leukemic blast cells. The Km values of dCYd and 2-F-araA for the cytoplasmic enzyme were and 213 .mu.M, respectively. At concentrations of 0.4 mM, the analog was phosphorylated 2.9 times faster than dCyd. The 5''-triphosphate of 2-F-araA was examined for its biochemical effects on partially purified ribonucleotide reductase and highly purified DNA .alpha.- and .beta.-polymerases from HeLa cells. 2-F-araATP was a potent inhibitor of ribonucleotide reductase; the concentration required for 50% inhibition of ADP reduction (0.3 mM ADP: 5 mM GTP or dGTP) was 1 .mu.M and for CDP reduction (0.15 mM CDP: 5 mM ATP) was 8.5 .mu.M. 2-F-araATP was a competitive inhibitor (Ki = 1.2 .mu.M) with respect to dATP (Km = 3.8 .mu.M) of DNA .alpha.-polymerase; DNA .beta.-polymerase was relatively insensitive to the drug. The cytotoxic actions of 2-F-araA may be due, in part, to a self-potentiating inhibition of DNA synthesis. That is, by inhibiting the formation of competing dATP, 2-F-araATP may potentiate its inhibition of DNA synthesis.