Partial purification and some properties of polyphenol oxidase extracted from litchi fruit pericarp
Yue-Ming Jiang, Giora Zauberman and Yoram Fuchs
Postharvest Biology and Technology Vol: 10 Issue: 3 Pages: 221-228.
1997
บทคัดย่อ
Litchi (Litchi chinensis Sonn.) fruit peel polyphenol oxidase (PPO)
was partially purified 21 fold by ammonium sulfate fractionation and gel
filtration. Pyrogallol, catechol, and 4-methylcatechol were good substrates for
the enzyme; with no activity observed with chlorogenic acid, p-cresol,
resorcinol, or tyrosine. The optimal pH for PPO activity was 7.0 with 4-methylcatechol,
with the enzyme being most stable at pH 7.4. The enzyme was relatively
temperature stable with maximum activity at 70°C and requiring a little less
than 10 min at 90°C for 50% loss of activity. The Km
and Vmax for the enzyme, with 4-methylcatechol, were 10 mM
and 1.47 ×
104 units/min per mg protein, respectively. The enzyme was not
activated by SDS. Reduced glutathione,-cysteine,
tropolone, thiourea, FeSO4, and SnCl2 markedly inhibited
PPO activity, whereas MnSO4 and CaCl2 enhanced PPO
activity. Data obtained in this study might help to better understand and
control commercially, litchi fruit peel browning.