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

Abstract

Polyphenol oxidase (PPO Y ) of edible yam (Dioscorea cayenensis-rotundata cv. Longboˆ) cultivated in Coˆte 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.

Biochemical Characterization of Two Polyphenol Oxidase Purified from Edible Yam (Dioscorea cayenensis-rotundata cv. Kponan) Cultivated in Côte d’Ivoire

“…Indeed, the anion exchange chromatography on a DEAE-Sepharose Fast Flow column enabled the enzyme activity to be separated into two different isoforms (PPO1 and PPO2), while hydrophobic interaction chromatography on Phenyl-Sepharose 6 Fast Flow led to separate each polyphenol oxidase from the other proteins and impurities. Similar results concerning Phenyl-Sepharose gel has been reported for the purification of polyphenol oxidase of yam tuber Dioscorea cayenensis-rotundata, cv Longbô [22] and polyphenol oxidase of apple (Malus domestica borkh. cv Bramley's seedling) [23].…”

“…Therefore, pH 6.0 and 6.6 is a good compromise between the activity and stability of these enzymes to perform oxidation of phenolic substrates over a long time. The proximate neutrality pH value determined for the two polyphenols was largely consistent with those reported for other polyphenol oxidases of banana pulp (6.5) [32], medlar fruits (Mespilus germanica L. Rosaceae) [33] and yam Longbô (6.6) [22]. From Arrhenius plot, values of 54.2±2.04 and 48.5±1.12kJ/mol were obtained as the activation energy of PPO1 and PPO2, respectively.…”

Thermodynamics and Kinetics of Thermal Inactivation of Polyphenol Oxidases and Peroxidase of Three Tissues (Cambium, Central Cylinder, Internal Bark) of Cassava Roots (Manihot esculenta CRANTZ) varietie Bonoua 2, Cultivated in Côte d’Ivoire

“…The high values of enthalpy obtained during thermal inactivation of these enzymes from the three tissues (cambium, central cylinder and internal bark) of cassava roots varietiebonoua 2 indicate that these enzymes undergo substantial conformational changes to be under their activated forms during the heat treatment (Gnangui et al, 2009). Moreover, positive values of the enthalpies suggest that the endothermic nature of the thermal inactivation reactions (Ozdes et al, 2009).…”

“…However, the negative values observed for the variation in entropy indicate that there are no significant processes of aggregation, since, if this would happen, the values of entropy would be positive (Anema and McKenna, 1996). They also indicate that these reactions are reversible (Gnangui et al, 2009). Negative values of entropy (ΔS # <0) obtained during thermal inactivation, naturally leads to higher values of free energy (ΔG # ).…”

Effect of thermal processing on oxide reductase inactivation and on colour fixing in erva‐mate (Ilex paraguariensis St. Hill) leaves

“…However, if the extraction is performed correctly, with appropriate solvent and short time, the losses are reduced. Due that, and also its low cost and practicality, the spectrophotometric method is widely adopted for the PPO and POD activity determination, as papers with banana fruits (Ünal et al ., 2007; Chaisakdanugull & Theerakulkait, 2009), apples (Buckow et al ., 2009), melons (Chisari et al , 2009), grapes (Núñez‐Delicado et al , 2007; Fortea et al ., 2009), aubergine (Dogan et al , 2002), celery (Aydemir & Akkanli, 2006), yam (Gnangui et al ., 2009), lilies (Yang & Wang, 2008), green coconut water (Murasaki‐Aliberti et al ., 2009) and others.…”