갈근 중의 Polyphenol Oxidase에 관한 연구

Studies on Polyphenol Oxidase from Puerariae Radix

  • 박수선 (숙명여자대학교 약학대학) ;
  • 김안근 (숙명여자대학교 약학대학) ;
  • 이정신 (숙명여자대학교 약학대학)
  • Park, Soo-Sun (College of Pharmacy, Sookmyung Women's University) ;
  • Kim, An-Keun (College of Pharmacy, Sookmyung Women's University) ;
  • Lee, Jeong-Sin (College of Pharmacy, Sookmyung Women's University)
  • 발행 : 1991.06.30

초록

Polyphenol oxidase(PPO) was purified from an extract of Puerariae Radix by ammonium sulfate fractionation followed by Sephadex G-150 column chromatography, which resulted in a 56-fold increase in specific activity. The enzyme was optimum of pH 6.5. The optimum temperature of enzymic reaction was about $40^{\circ}$. The enzyme was thermostable with a half-life equal to 32 min at $70^{\circ}$. Km values of the PPO for catechol and pyrogallol from Lineweaver Burk plots were $1.3{\times}10^{-2}M$, $1.16{\times}10^{-2}M$, respectively. The substrate specificity of the Puerariae Radix PPO showed high affinity toward pyrogallol. Reducing reagents such as cysteine, potassium metabisulfite, ascorbic acid, 2-mercaptoethanol completely inhibited the PPO activity at $10^{-2}M$ level. Linewear-Burk analysis of inhibition data revealed that the inhibition by cysteine, 2-mercaptoethanol, 4-nitrocatechol, potassium cyanide was competitive with Ki values of $4.3{\times10^{-2}M,\;0.73{\times}10^{-6}M,\;6.9{\times}10^{-6}M,\;6.4{\times}10^{-7}M$, respectively. The browning reaction by PPO was observed to decrease temporarily with the addition of sodium diethyl dithiocarbamate, a well known copper chelating agent. Among the divalent cations, $Cu^{2+}$ ion was strong activator on PPO and $Mn^{2+},\;Co^{2+}$ ions was effect on PPO activity. $Zn^{2+},\;Mg^{2+}$ ions was inhibitor on PPO.

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