The biochemical characteristics of polyphenol oxidase from browning tissue-cultured bamboo (Dendrocalamus latiflorus)
1999
Wu, H.C. | Chu, H.L. | Kuo, J.M. | Huang, L.C. | Shaw, J.F.
Polyphenol oxidase (PPO) was isolated and purified 107 fold from browning bamboo tissue (Dendrocalamus latiflorus) using DEAE-Sepharose CL-6B ion exchange, Octyl-Sepharose CL-4B hydrophobic interaction chromatography, and gel filtration on Sephacryl S-300. The apparent molecular mass was estimated to be 92 kDa by 3-20% polyacrylamide gel electrophoresis. The optimal pH of PPO was 8.0, and the optimal temperature was 65 degrees C when L-DOPA was used as the substrate. PPO activity was stimulated by Cu2+ at 5 mM to a maximal activity of about 2.1 fold. L-cysteine, sodium sulfite, ascorbic acid and sodium diethylthiocarbamate were found to be potent inhibitors of PPO. Since sodium diethylthiocarbamate is a specific chelator of Cu2+, these results suggested that Cu2+ ion must be present in the active site of the enzyme. PPO showed low cresolase activity, and diphenols were the preferred substrate.
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