Some characteristics of polyphenol oxidase purified from edible yam (Dioscorea cayenensis-rotundata cv. Longbô) cultivated in Côte d'Ivoire

Polyphenol oxidase (PPO_Y) of edible yam ( Dioscorea cayenensis-rotundata cv. Longbô ) cultivated in Côte d'Ivoire was purified to homogeneity by a procedure that included ion exchange chromatography, ammonium sulphate fractionation, gel filtration and hydrophobic chromatography using dopamine as a substrate. The relative molecular weight of the PPO_Y was estimated to be 94.75 ± 0.63 and 151.56 ± 2.75 kDa by SDS–PAGE and gel filtration on Sephacryl S100 HR, respectively, indicating this PPO_Y as a multimer. Maximal PPO_Y activity occurred at 30 °C and pH 6.6. The enzyme was stable at 25 °C and its pH stability was in the range of 6.0–7.0. The values V _max/ K _m showed that the enzyme had the greatest reactivity towards dopamine among the substrates used. PPO_Y showed no activity toward the monophenols and was completely inhibited by beta-mercaptoethanol, sodium thiosulphate, l -ascorbic acid, sodium bisulphite and l -cysteine. Data generated by this study might help to better prevent edible yam browning.