• Korean Journal of Pharmacognosy
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• v.20 no.2
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• pp.101-109
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• 1989

Purification of polyphenol oxidase(PPO) from Korean native tobacco variety leaves was carried out through the procedure of acetone preciptation, ammonium sulfate fractionation, and Sephadex G-150 gel filtration, resulting in a 84-fold increase in specific activity. The enzyme was stable in a range of pH 7.5 to 8.0 with an optimum of pH 7.5. The optimum temperature for the enzymic reaction was about $60^{\circ}$. It was thermostable with a half-life equal to 20 min at $70^{\circ}$. Km values for (+)-catechin and pyrogallol were $1.6{\times}10^{-3}$ and $0.5{\times}10^{-3}M$, respectively. It possesses high catecholase activity but little or no cresolase activity. Lineweaver-Burk analysis of inhibition data revealed that the inhibition of (+)-catechin oxidation by potassium cyanide, 4-nitrocatechol, cystein and 2-mercaptoethanol was competitive with Ki values of $1.1{\times}10^{-6}$, $1.8{\times}10^{-6}$, $8.9{\times}10^{-6}$ and $1.3{\times}10^{-5}$, respectively.