Different effects of vanadium ions on some DNA-metabolizing enzymes

The effects of vanadium on some enzymes involved in DNA metabolism were investigated in vitro. Vanadate (V) ions competitively inhibit calf thymus terminal deoxynucleotidyl transferase with Ki = 2.5 microM. A binding of vanadium to the enzyme with no change of the amount of the Zn constituent of the protein was found at concentrations of vanadate causing inhibition. The catalytic activity of mammalian DNA polymerase alpha was also inhibited by vanadate ions at an I50 of 60 microM, while the bacterial (E. coli) DNA polymerase I was affected to the same extent only when the concentration of vanadate was raised to about 0.5 mM. In contrast to the inhibitory effects caused by vanadium on the nucleotidyl transferases, concentrations of pentavalent vanadium ions of the order of 10 microM increase 2.4-fold the hydrolytic activity of deoxyribonuclease I from bovine pancreas. These findings suggest that vanadium can interact with enzymes involved in nucleic acid metabolism.