Purification and Characterization of a Polyphenol Oxidase from Cimin Grape (Vitis vinifera spp., Cimin)

A polyphenol oxidase (PPO) from Cimin grape was purified 11.2-fold by using a Sepharose 4B-L-tyrosine-p-aminobenzoic acid affinity column. The optimum pH and temperature of PPO purified from Cimin grape were 7.5 and 30 degrees C respectively. The apparent Km was 19.5 mM and V-max was 2378U/mg protein. Ascorbic acid and sodium metabisulfite were potential inhibitors. Enzyme stability was higher than for most PPOs purified from other sources, with 90% of original activity retained after incubation for 2 hours at 80 degrees C. The activity of the enzyme increased by 145.7 +/- 2.0%, 138.7 +/- 2.4% and 130.5 +/- 1.4% in the presence of 1 mM Ca2+, Ni2+ and Co2+ respectively. This study gives essential information about Cimin grape PPO, an enzyme affecting the shelf-life of the fruit.