Abstract

The inhibitory effect of daunorubicin on the enzymatic degradation of DNA was studied in vitro. The initial kinetics of acid deoxyribonuclease (deoxyribonucleate 3'-nucleotidohydrolase, EC 3.1.4.6) degradation was investigated using analytical ultracentrifugation to determine the ratio of single-strand to double-strand breaks. The late phase of the degradation was followed by hyperchromicity. Evidence is presented that the mechanism of inhibition of DNase activity involves nonproductive binding of daunorubicin-intercalated DNA. Calculations show that total inhibition occurs when 1 molecule of the antibiotic binds per 10 nucleotides.