title: DNA-cleaving activity of superoxide dismutase specific for circular supercoiled double-stranded DNA in vitro.
abstract: 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 H2O2 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 O2- dismutation site of SOD. The enzymatic mechanism of cleaving activity of SOD to supercoiled DNA was discussed.
authors.affiliation: Shanghai Institute of Biochemistry, Academia Sinica, P.R. China.
authors.forename: J
authors.initials: J
authors.lastname: Ling
authors.forename: X
authors.initials: X
authors.lastname: Gao
authors.forename: W Y
authors.initials: WY
authors.lastname: Liu
authors.forename: K C
authors.initials: KC
authors.lastname: Ruan
mesh_terms: D000818:Animals; D002417:Cattle; D004247:DNA / Q000187:drug effects*; D004278:DNA, Superhelical / Q000187:drug effects*; D004912:Erythrocytes / Q000201:enzymology; D019791:Guanidine / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D010947:Plants, Toxic; D010957:Plasmids; D013482:Superoxide Dismutase / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D013552:Swine; D014026:Nicotiana / Q000201:enzymology
chemical_list: D004278:DNA, Superhelical; D004247:DNA; D006861:Hydrogen Peroxide; D013482:Superoxide Dismutase; D019791:Guanidine