• Applied Biological Chemistry
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• v.35 no.3
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• pp.170-172
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• 1992

Four types of polyphenol oxidase were isolated from the crude extract of a Ligularia fischeri by gel filtration on Sephadex G-150. Optimum pH and temperature for the activity of partially purified enzyme were 7.5 and $25^{\circ}C$, respectively. It was stable at temperature $40^{\circ}C$ when examined at pH 7.5 for 5 min, and lost 90% of its activity at $70^{\circ}C$ in 30 min at pH 7.5. The enzyme has good activity on catechol and chlorogenic acid but was inactive on dopamine.

• Food Science and Biotechnology
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• v.16 no.3
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• pp.421-425
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• 2007

The inhibitory effect of onion extract on polyphenol oxidase (PPO) and browning of peach juice was investigated. Various reducing agents such as L-ascorbic acid, L-cysteine, dithiothreitol, glutathione, and sodium pyrosulfite strongly inhibited polyphenol oxidase extracted from peach. The enzyme was also inhibited by addition of water extract of onion. Regardless of substrates used, the addition of heated onion extract exhibited stronger inhibitory effect on peach polyphenol oxidase activity than that of the fresh one. The inhibitory effect of onion extract was dependent on heating temperature and time. The onion extract inhibited the peach polyphenol oxidase non-competitively. The heating of onion extract in the presence of glucose, glycine stimulated the inhibitory effect of the onion extract, which suggests non-enzymatic browning products produced during heating might be responsible for the stronger inhibitory action of the heated onion extract. The retardation of peach juice browning by onion extract seems to be caused by inhibition of peach PPO.

• Applied Biological Chemistry
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• v.24 no.3
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• pp.167-173
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• 1981

Crude enzyme of polyphenol oxidase was obtained from garlic. This enzyme actively oxidized triphenols such as pyrogallol and gallic acid, although it showed very weak activity on diphenols such as catechol and chlorogenic acid among the phenolic compounds tested. The optimum pH of the enzyme was 6.5 which was slightly higher than that of the garlic itself (pH 6.0). The enzyme was stable relatively at heat treatment. Sodium metabisulfite inhibited the enzyme activity at the concentration of 1mM, and KCN, L-ascorbic acid and thiourea also inhibited the enzyme action. $Mg^{++}$ activated the enzyme activity. $Cu^{++}$ activated slightly the enzyme action at low concentration (1mM), but inhibited at high concentration (10mM).

• Korean Journal of Food Science and Technology
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• v.23 no.4
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• pp.414-419
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• 1991

Polyphenol oxidase from Jerusalem artichoke(Helianthus tuberosus L.) tubers was partially purified by precipitation with ammonium sulfate, followed by gel filtration on Sephadex G-100. The enzyme showed maximal activity at pH 6.5 and $4^{\circ}C$. Kinetic studies indicated $K_{m}$ value of 3 mM for catechol and activation energy of 72.6 kcal/mole. As for substrate specificity of polyphenol oxidase the enzyme showed high affinity towards diphenol compounds, but not towards monophenols. The enzamatic browning was completely inhibited at 1 mM concentration of L-ascorbic acid, sodium hydrosulfite and L-cystein(HCl). The activity of polyphenol oxidase in 0.1 M potassium phosphate buffer(pH 6.5) was fairly stable for a week at $4^{\circ}C$, while it decreased remarkably at $25^{\circ}C$.

• Journal of the Korean Society of Food Science and Nutrition
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• v.13 no.4
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• pp.397-402
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• 1984

As a basic research for inhibition of enzymatic browning of apple wine, polyphenol oxidase (EC 1.10.3.1) from apple (Jonathan) was extracted, partially purified, and some properties of the enzyme and changes o( active bands by heat treatment were investigated. Optimum conditions for the enzyme reaction were pH6.5 and temperature of $30^{\circ}C$, and o-diphenol was the main substrate for the enzyme. Approximately 35% and 15% of initia lpolyphenol oxidase activity remained after heating at $60^{\circ}C$ and $70^{\circ}C$ for 1 hour, respectively. About 0.5mM of the inhibitor such as sodium metabisulfite, cysteine and ascorbic acid was required for effective inhibition of the enzyme reaction. However, EDTA was found to be a very poor inhibitor. Ethanol did not affect the enzyme activity. The number of active bands of polyphenol oxidase from apple(Jonathan) was found to be four, but two bands and one band were observed after heating at $60^{\circ}C$ and $70^{\circ}C$ for 1 hour, respectively, which showed a significant difference in thermal stability among active bands.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.3
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• pp.289-295
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• 2007

This study was conducted to investigate the potential of polyphenols and polyphenol oxidase activity on the induction of rusty symptom development in ginseng root. When rusty inducing bacteria were inoculated on fresh ginseng root, the hue value of the inoculated root increased from 101.2 (white yellow) at 1 day after innoculation to 60.9 (brownish red) at 30 days after innoculation. Lysobacter gummosus, Pseudomonas veronii and Agrobacterium tumefaciens enhanced the accumulation of total phenolics. Along with the increase of total phenolics, total activity of polyphenol oxidase concomitantly increased but the specific activity of the enzyme was not.

• Journal of the Korean Society of Food Science and Nutrition
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• v.12 no.4
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• pp.316-322
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• 1983

In order to obtain elementary data of enzymatic browning of apples and apple products and to examine effectively inhibitory method of browning, we extracted polyphenol oxidase (EC 1.10.3.1) from apple (Ralls Janet) and investigated its general properties. The optimum conditions for the enzyme reaction were pH 6.0 and temperature of $30^{\circ}C$. The enzyme was very stable at pH 4.0, and at the range of pH 5.0-9.0 its activity was above 80% compared with pH 4.0. The enzyme was very stable by heating at $40^{\circ}C$ for 1 hour, and almost 50% of enzyme activity was lost by heating at $60^{\circ}C$ for 30 minutes. The polyphenol oxidase activity was enhanced by the addition of $Cu^{2+}$ and $Mn^{2+}$, respectively, meanwhile $Na^+$, $Hg^{2+}$ and $Co^{2+}$ inhibited the enzyme activity. The enzyme activity was greatly decreased in the presence of inhibitors such as cysteine, sodium metabisulfite and ascorbic acid. The polyphenol oxidase greatly catalyzed the oxidation of o-diphenols such as chlorogenic acid and catechol, which suggests that main substrate of polyphenol oxidase is o-diphenol compounds.

• Korean Journal of Food Science and Technology
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• v.34 no.4
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• pp.552-558
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• 2002

Polyphenol oxidase from Flammulina velutipes was purified and characterized. Purification of polyphenol oxidase was achieved by ammonium sulfate precipitation, Superdex G-200 gel filtration chromatography, Phenyl superose affinity chromatography, Mono-Q anion exchange chromatography and Superdex S-200 gel filtration chromatography on FPLC. After these purification steps specific activity of purified polyphenol oxidase increased to 199.1 units/mg. Polyphenol oxidase from F. velutipes was composed of a single polypeptide with molecular weight of about 40 kDa. Optimum pH and temperature for the enzyme reaction were found to be 6.0 and $25^{\circ}C$, respectively. The activity of the enzyme gradually decreased at acidic pH between 3 and 5, and the enzyme lost its activity at alkaline pH between 8 and 10. This enzyme exhibited high substrate specificity to o-diphenols. Km-values for L-DOPA and caffeic acid were found to be 3.97 mM and 1.78 mM, respectively. 2-mercaptoethanol, L-ascorbic acid, sodium bisulfite, EDTA and $Mg^{2+}$ inhibited the activity of pholyphenol oxidase and $Cu^{2+}$, $Fe^{2+}$, $Zn^{2+}$ and $Ni^{2+}$ increased enzyme activity. The activity of enzyme was well maintained at $-70^{\circ}C$ for over 4 months, and at $-20^{\circ}C$ for 1 months.

• Food Science and Preservation
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• v.12 no.5
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• pp.489-495
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• 2005

Polyphenol oxidase (PPO) from Burdock (Arctium lappa L.) was purified and characterized. Purification of polyphenol oxidase was achieved by ammonium sulfate precipitation, Phenyl-sepharose CL-4B hydrophobic chromatography and Sephadex G-100 gel filtration chromatography. The molecular mass of the purified PPO was estimated to be 30 kDa by SDS polyacrylamide gel electrophoresis. In a substrate specificity, maximum activity was achieved with chlorogenic acid, followed by catechol and catechin. Whereas, there was low activity with hydroquinic acid, resorcinol or tyrosine. The optimum pH and temperature for enzyme activity were 7.0 and 35$\circC$ with catechol, respectively. The enzyme was most stable at pH 7.0 while unstable at acidic and alkaline pH. The enzyme was stable when heated to 40$\circC$. But heating at 50$\circC$ for more than 30 min caused 50% loss of activity. Ascorbic acid, L-cystein and $Cu^{2+}$ inhibited the activity of pholyphenol oxidase.

• Korean Journal of Food Science and Technology
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• v.16 no.4
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• pp.413-417
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• 1984

To examine enzymatic browning of apple wine, changes of active bands of polyphenol oxidase (EC 1.10.3.1) as well as polyphenol substances related to browning of apple wine were investigated during wine brewing. The decrease of total phenol was remarkably inhibited by the addition of sodium metabisulfite. In the meantime, auto-oxidation of catechol in a model system increased proportionally as the reaction pH and temperature increased. Catechol oxidation, however, was not detected at $4^{\circ}C$ below pH 5.0. Polyacrylamidegel electrophoretic patterns showed that the apple (Jonathan) indicated 4 bands with polyphenol oxidase activity, designated a, b, c and d whose Rm were 0.21, 0.30, 0.41 and 0.51, respectively. Among these, 2 bands, a and c remained until 5th day fermentation and only c band after 6th day fermentation. After pasteurization of apple wine at $60^{\circ}C$ for 30min, c band also remained.