Abstract: There were Mn-SOD,Fe-SOD and CuZn-SOD in the crude extract of Citrus erythrosa Tanaka leaves.In a 10% PAGE three active bands were seen,and R fvalue of Mn-SOD was big than that of Fe-SOD and was same as that of CuZn-SOD₁.While in a 4%~35% gel concentration gradient electrophoresis,four active bands were seen and Mn-SOD's R fvalue was the smallest.This means that the molecular weight of Mn-SOD was the biggest and it had a high charge density.Mn-SOD,which occupied about 20% of the total SOD activity,was purified to homogeneity by means of ammonium sulfate precipitation,Sephadex G-100 gel filtration,DEAE-Sepharose and CMsub>52 chromatography etc.Its specific activity was 1 249 U/mg.Its molecular and subunit weight were 54.0 kD and 26.6 kD,respectively.It had one absorption maximum which was at 280 nm.And it was stable to heat treatment,46% of its activity was retained at 95℃ for 15 min.Isoelectric focusing electrophoresis showed that it had a pI of 5.06.This enzyme was insensitive to KCN and H₂O₂,but was sensitive to 1% SDS or mixtures of chloroform and ethanol (3:5 v/v).

Key words: Citrus erythrosa Tanaka, Mn-SOD, purification, characterization, charge density