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Properties of wheat bran polyphenol oxidase

✍ Scribed by Soysal, Çi??dem ;Söylemez, Zerrin

Publisher
John Wiley and Sons
Year
2004
Tongue
English
Weight
232 KB
Volume
48
Category
Article
ISSN
0027-769X

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✦ Synopsis

Abstract

Polyphenol oxidase (PPO) obtained from wheat bran catalyzed the oxidation of 4‐methyl catechol. Phenolic compounds found naturally in crude extract played role as an endogeneous substrate and activity of crude extract needed correction. Activity versus enzyme concentration gave a linear plot at high substrate concentration whereas a nonlinear plot was obtained at low substrate concentration which proved the presence of endogeneous substrate. Adsorption on celite and extraction with polyvinylpyrrolidone (PVPP) caused the removal of phenols. Adsorption of PPO on celite yielded a 4‐fold increase in specific activity whereas extraction with PVPP yielded a 2.5‐fold increase in specific activity compared to the crude extract. The kinetics of PPO catalyzed oxidation obeyed Michaelis‐Menten model; K~m~ and V~max~ values were found as 218 mM and 99 μM/min, respectively. The enzyme was inhibited by ethyl alcohol, dithiothreitol (DTT) and isoproterenol and exhibited heat stability up to a temperature of 90°C. The optimum pH of the enzyme was found to be 5.0.

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