Terminal deoxynucleotidyl transferase catalyzes the reaction of DNA phosphorylation.

The reaction of phosphorylation and phosphonylation of an oligodeoxynucleotide 3'-terminal hydroxyl (oligodeoxynucleotidyl kinase activity) catalyzed by calf thymus terminal deoxynucleotidyl transferase (TDT) was found. Triphosphates modified at Palpha-, Palpha,gamma- or Palpha,beta,gamma-residues served as low-molecular weight substrates. The reaction was TDT specific; human DNA polymerasesalphaandbeta, as well as AMV reverse transcriptase did not catalyze it. The donor activity of modified triphosphates or triphosphonates depended on their structure and was increased with an increase in their hydrophobicity. The substrate activity of some modified triphosphates was up to one order of magnitude higher than that of ddTTP.