DNA-cleaving activity of superoxide dismutase specific for circular supercoiled double-stranded DNA in vitro

• Published in: The international journal of biochemistry & cell biology 1998-10, Vol.30 (10), p.1123-1127
• Main Authors: Ling, Jun, Gao, Xiang, Liu, Wang-Yi, Ruan, Kang-cheng
• Format: Article
• Language: English
• Subjects: Animals; Bovine erythrocyte Cu/Zn-SOD; Cattle; DNA - drug effects; DNA, Superhelical - drug effects; Erythrocytes - enzymology; Guanidine - pharmacology; Hydrogen Peroxide - pharmacology; N. tabacum Mn-SOD; Nicotiana - enzymology; Plants, Toxic; Plasmids; Porcine erythrocyte Cu/Zn-SOD; Supercoiled DNA-cleaving activity; Superoxide Dismutase - chemistry; Superoxide Dismutase - isolation & purification; Superoxide Dismutase - pharmacology; Swine
• ISSN: 1357-2725; 1878-5875
• DOI: 10.1016/S1357-2725(98)00072-7

Several superoxide dismutases (SODs), N. tabacum Mn-SOD, porcine erythrocyte Cu/Zn-SOD and bovine erythrocyte Cu/Zn-SOD, have been found to exhibit the activity to cleave the circular supercoiled double-stranded DNA into nicked and further linear form in vitro. The fact that porcine erythrocyte Cu/Zn-SOD did not cleave the linear double-stranded DNA excluded the possibility that nuclease contaminated the SOD preparations and showing the cleaving activity was dependent on the supercoiled form of DNA. Porcine erythrocyte Cu/Zn-SOD inactivated by H 2O 2 or guanidine still remained its supercoiled DNA-cleaving activity. However, when the SOD was digested with proteases, its activity to cleave supercoiled DNA was completely abolished. These results suggested that the supercoiled DNA-cleaving activity was relative to the apoenzyme moiety, less relevant to the O 2 − dismutation site of SOD. The enzymatic mechanism of cleaving activity of SOD to supercoiled DNA was discussed.