A peroxidase was purified by gel filtration and SDS-PAGE homogeneity from Ipomoea cairica leaves using ammonium sulphate precipitation acetone fractionation, and gel filtration chromatography on Sephadex G-100 and Sephadex G-200 columns. The enzyme was purified about 51 times with a recovery of 84%. It was a glycoprotein (carbohydrate content 35%) containing two isoenzyme components of identical molecular mass, but differing in surface electrical properties when checked by SDS-PAGE and PAGE observations. Amino acid analysis indicated that the purified enzyme preparation did not contain methionine. The enzyme was stable at 60 degrees C, and in the pH range 5-11. Some metal ions (Ag+, Fe2+, Fe3+, Hg2+) inhibited the enzyme. The enzyme may be of use as a diagnostic reagent in assays for glucose in place of commercially available horseradish peroxidase.