Purification and characterization of polyphenol oxidase (PPO) from water yam (Dioscorea alata)

Abstract

Polyphenol oxidase (PPO) is responsible for the enzymatic browning of fruits and vegetables, and thus has negative effects on the quality of food. In this study, extraction and purification of PPO from water yam was performed successfully, and the characteristics of PPO and inhibitors of enzyme activity were analysed. The results showed that PPO activity improved by 4.58-fold through the DEAE-Sepharose and Superdex G-75 purification technique, which reached electrophoretic purity. The enzyme molecular weight was estimated to be 32 kDa. The optimum pH and temperature values of PPO were 6.0 and 35°C, respectively, and it was not thermostable at higher temperatures. PPO had the highest substrate affinity towards catechol (Km = 27.82 mmol/L and Vmax = 1.464 △A/ min). The most effective inhibitor was L-cysteine followed by ascorbic acid and sodium sulfite. Purificación y caracterización de la polifenol oxidasa (PPO) obtenida del ñame de agua (Dioscorea alata) RESUMEN La polifenol oxidasa (PPO) es responsable del pardeamiento enzimático de frutas y verduras; por lo tanto, tiene efectos negativos en la calidad de los alimentos. En el presente estudio se extrajo y se purificó con éxito la PPO proveniente del ñame de agua, y se analizaron sus características y los inhibidores de la actividad enzimática. En este sentido, los resultados indicaron que la actividad de la PPO mejoró 4.58 veces al emplear la técnica de purificación DEAE-Sepharose y Superdex G-75, que alcanzó la pureza electroforética. El peso molecular de la enzima se estimó en 32 kDa. Los valores óptimos de pH y temperatura de la PPO fueron 6.0 y 35°C, respectivamente, constatándose que no era termoestable a temperaturas más altas. La PPO mostró mayor afinidad de sustrato hacia el catecol (Km = 27.82 mmol/L y Vmax = 1.464 △A/min). Su inhibidor más efectivo fue la L-cisteína, seguida por el ácido ascórbico y el sulfito de sodio.

Purification, kinetic parameters, and isoforms of polyphenol oxidase from “Xushu 22” sweet potato skin

“…The pH optimum of sPPO1 was 6.6 which is close to the pH optima seen for thyme and green Small cherry tomato ( Solanum lycopersycum ) PPOs (Dogan & Dogan, 2004; Saeidian & Rashidzadeh, 2019). For sPPO2 the optimum pH was 6.0, which is the same pH optima seen for water yam ( Dioscore alata ) PPO (Peng et al., 2019). It should be noted that enzyme source, nature of phenolic substrates, extraction methods, oxidation mechanism, structural difference, and localization were responsible for the difference of optimal pH of isozymes (Han et al., 2019; Montero, Ávalos, & Pérez‐Mateos, 2001; Yoruk & Marshall, 2003).…”

“…The vast majority of plant‐derived PPOs have a pH optimum between 4.5 and 8.0 (Peng et al., 2019; Ünal & Şener, 2016; Wang et al., 2007; Zawistowski, Biliaderis, & Murray, 1988). Compared with previous literature reports, the pH optimum for mPPO was 7.4, which is closer to that seen for Izmir grapes PPO (Önez, Karakuş, & Pekyardimci, 2008).…”

Effects of Different Storage Conditions on the Browning Degree, PPO Activity, and Content of Chemical Components in Fresh Lilium Bulbs (Liliumbrownii F.E.Brown var. viridulum Baker.)

“…This led to the increased MDA content and accumulation of phenolic compounds, which provided sufficient substrate for enzymatic reaction in the early stage of storage (until the 6th day). At the same time, this temperature was within the best activity temperature range of PPO, and therefore, PPO activity increased [54]. These factors caused the browning degree of G3 to be higher than that of G1 and G2.…”

Purification, Characterization, and Inhibition of Tyrosinase from Jerusalem Artichoke (Helianthus Tuberosus L.) Tuber

“…The optimum pH of Artichoke tyrosinase was found to be 7.0 (26). Moreover, the optimal pH of water yam and tea leaves enzyme was found to be 6.0 and 8.0 respectively (30)(31). Alike results were also reported where enzyme revealed a maximum activity at 30 o C for flesh of Turkish Jerusalem Artichoke (25), and eggplants (32).…”