Isolation,Purification and Enzymological Properties of Peroxidase from Sweet Potato(Ipomoea batatas Lam.) Leaves

In order to obtain purified peroxidase from sweet potato(Ipomoea batatas Lam.) leaves for the study of its enzymatic properties,ammonium sulfate precipitation,ion exchange chromatography on DEAE-Sepharose column and Sephacryl S-200 gel filtration were used to purify peroxidase(POD) from sweet potato leaves.The specific activity of purified POD was 91923.14 U/mg,which exhibited a purification fold of 255.69 and a recovery rate of 1.59%.The molecular weight of this enzyme was 35 kD,and the optimal pH and temperature were 5.6 and 60 ℃,respectively.The peroxidase was stable at 20-50 ℃ and pH 4-8.The apparent Km of this enzyme using H2O2 as substrate at different conditions was 0.291 mol/L at 25 ℃ and pH 7.2.Its activity was enhanced by urea,Li+,Na+,K+,Mg2+ and oxalic acid,yet inhibited by SDS,KSCN,AsA(ascorbic acid) and Mn2+.Organic solvents such as methanol,ethanol,glycol and isopropanol could inhibit the activity of this enzyme and the order according to the inhibitory effect from strong to weak was isopropanol,ethanol,methanol and glycol.These results reveal that POD is very stable and therefore has promising application value.