Novel Hydrogen Peroxide Metabolism in Suspension Cells ofScutellaria baicalensis Georgi

• Published in: The Journal of biological chemistry 1998-05, Vol.273 (20), p.12606-12611
• Main Authors: Morimoto, Satoshi, Tateishi, Norifumi, Matsuda, Tomoko, Tanaka, Hiroyuki, Taura, Futoshi, Furuya, Naruto, Matsuyama, Nobuaki, Shoyama, Yukihiro
• Format: Article
• Language: English
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.273.20.12606

We identified a rapid and novel system to effectively metabolize a large amount of H2O2 in the suspension cells ofScutellaria baicalensis Georgi. In response to an elicitor, the cells immediately initiate the hydrolysis of baicalein 7-O-β-d-glucuronide by β-glucuronidase, and the released baicalein is then quickly oxidized to 6,7-dehydrobaicalein by peroxidases. Hydrogen peroxide is effectively consumed during the peroxidase reaction. The β-glucuronidase inhibitor, saccharic acid 1,4-lactone, significantly reduced the H2O2-metabolizing ability of theScutellaria cells, indicating that β-glucuronidase, which does not catalyze the H2O2 degradation, plays an important role in the H2O2 metabolism. As H2O2-metabolizing enzymes, we purified two peroxidases using ammonium sulfate precipitation followed by sequential chromatography on CM-cellulose and hydroxylapatite. Both peroxidases show high H2O2-metabolizing activity using baicalein, whereas other endogenous flavones are not substrates of the peroxidase reaction. Therefore, baicalein predominantly contributed to H2O2 metabolism. Because β-glucuronidase, cell wall peroxidases, and baicalein pre-exist inScutellaria cells, their constitutive presence enables the cells to rapidly induce the H2O2-metabolizing system.