Effects of Acid and Temperature on the Activity of Bleomycin

Abstract

The ability of bleomycin to decrease the melting temperature (T_m) of deoxyribonucleic acid (DNA) in the presence of 1, 2-benzenediol (catechol) was enhanced by previous storage of bleomycin in a solution of pH 3.0 for 3 h. Although this enhancement was also caused by adding water which was repeatedly (5 times) adjusted to pH 3.0 and then back to 7.4 without bleomycin, it was lost by further storage for 24 h at 37°C after neutralization to pH 7.4. These findings suggest that the activity of bleomycin may be indirectly enhanced by acid. The present result that bleomycin could effectively break the DNA strand at 60°C in comparison with other temperatures tested shows that the drug can preferentially interact with the loose helix of DNA.