Abstract
SummaryPolyphenol oxidase (PPOY) 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 PPOY 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 PPOY as a multimer. Maximal PPOY 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 Vmax/Km showed that the enzyme had the greatest reactivity towards dopamine among the substrates used. PPOY 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.
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