Characterization of peroxidase in buckwheat seed

• Published in: Phytochemistry (Oxford) 2006-02, Vol.67 (3), p.219-224
• Main Authors: Suzuki, Tatsuro, Honda, Yutaka, Mukasa, Yuji, Kim, Sun-ju
• Format: Article
• Language: English
• Subjects: Ascorbic Acid - chemistry; Ascorbic Acid - metabolism; Benzothiazoles; Biological and medical sciences; Buckwheat; Characterization; Dianisidine - chemistry; Dianisidine - metabolism; enzyme activity; enzyme kinetics; Enzyme Stability; Enzymes; Fagopyrum - enzymology; Fagopyrum esculentum; Fundamental and applied biological sciences. Psychology; grain crops; Guaiacol - chemistry; Guaiacol - metabolism; Hydrogen-Ion Concentration; Isoenzymes - chemistry; Isoenzymes - isolation & purification; Isoenzymes - metabolism; isozymes; Kinetics; Metabolism; molecular weight; Peroxidase; Peroxidase - chemistry; Peroxidase - isolation & purification; Peroxidase - metabolism; Plant physiology and development; plant proteins; Polygonaceae; Quercetin - chemistry; Quercetin - metabolism; Seed; seeds; Seeds - enzymology; Sulfonic Acids - chemistry; Sulfonic Acids - metabolism; Temperature; thermal stability; Tissue Distribution
• ISSN: 0031-9422; 1873-3700
• DOI: 10.1016/j.phytochem.2005.11.014

A peroxidase was purified from buckwheat seed, and characteristics (such as isozyme composition, molecular weight, substrate specificity, K m, thermal stability and organ distribution) were investigated. A peroxidase (POX)-containing fraction was purified from buckwheat seed. The POX consisted of two isozymes, POX I and POX II, that were purified 6.6- and 67.4-fold, respectively. Their molecular weights were estimated to be 46.1 kDa (POX I) and 58.1 kDa (POX II) by gel filtration. While POX I and II each oxidized quercetin, o-dianisidine, ascorbic acid and guaiacol, only POX II oxidized ABTS. Kinetic studies revealed that POX I and II had lower K m values for quercetin (0.071 and 0.028 mM), ABTS (0.016 mM for POX II) and ascorbic acid (0.043 and 0.029 mM) than for o-dianisidine (0.229 and 0.137 mM) and guaiacol (0.288 and 0.202 mM). The optimum pHs of POX I and II for various substrates were almost the same, except for quercetin; pH 8.0 for POX I and pH 4.5 for II. Their optimal temperatures were 30 °C (POX I) and 10 °C (POX II), and POX I was more stable than POX II above 30 °C.