Isolation and characterization of a mung bean leaf polyphenol oxidase

Crude extracts from mung bean leaves, roots, stems and dark grown seedlings contained multiple forms of polyphenol oxidase (PPO) with subunit M r values of 65 × 10 3, 59 × 10 3, 52 × 10 3, 47 × 10 3, 31 × 10 3 and 21 × 10 3. Only two of these forms were present in broken and intact leaf chloroplasts...

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Bibliographic Details
Published in:Phytochemistry (Oxford) 1997-05, Vol.45 (1), p.15-21
Main Authors: Shin, Ron, Froderman, Tim, Flurkey, William H.
Format: Article
Language:English
Subjects:
Biological and medical sciences
Enzymes
Fundamental and applied biological sciences. Psychology
Metabolism
Plant physiology and development
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Summary:Crude extracts from mung bean leaves, roots, stems and dark grown seedlings contained multiple forms of polyphenol oxidase (PPO) with subunit M r values of 65 × 10 3, 59 × 10 3, 52 × 10 3, 47 × 10 3, 31 × 10 3 and 21 × 10 3. Only two of these forms were present in broken and intact leaf chloroplasts. A mature form of PPO, purified to apparent homogeneity from leaf chloroplasts, contained two proteins with subunit M r values of 65 × 10 3 and 59 × 10 3, respectively. The purified enzyme had a pH optimum of 6.0, a pI of 5.1, and oxidized a variety of o-diphenols. The K m for l-dopa was 24 mM. o-Diphenol oxidation was inhibited by salicyl hydroxamic acid and 2,3-naphthalenediol, whereas methimazole, tropolone and 4-hexylresorcinol only resulted in partial inhibition.
ISSN:0031-9422
1873-3700
DOI:10.1016/S0031-9422(96)00785-6