Occurrence of a terminal deoxynucleotidyl transferase-like activity in N-2-fluorenylacetamide-treated rat liver.

A new enzyme activity that resembles terminal deoxynucleotidyl transferase (TdT-like activity) was found in rat liver. Upon treatment of rats with a hepatocarcinogen, N-2-fluorenylacetamide, the TdT-like activity increased in parallel with DNA polymerase Ci and 'Y. By phosphocellulose column chromatography, the TdT-like activity was separated from DNA polymerase Ci, fJ, and 'Y. With a poly(dA)-initiator, dGTP or dCTP was the most efficient substrate in the presence of Mg2+ or Mn2+, respectively. In the presence of Mg2+, the enzyme utilized poly (dC) as an initiator most efficiently. The TdT-like activity differed from previously described terminal deoxynucleotidyl transferase (E.e. 2.7.7.31.) in its Km value for dGTP and in its sensitivity to ATP or to an antibody against calf thymus terminal deoxynucleotidyl transferase.