Suzuki Tatsuro, Honda Yutaka, Mukasa Yuji, Kim Sun-Ju
National Agriculture Research Center for Hokkaido Region, Shinsei, Memuro, Kasai, Hokkaido 082-0071, Japan.
Phytochemistry. 2006 Feb;67(3):219-24. doi: 10.1016/j.phytochem.2005.11.014. Epub 2006 Jan 3.
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 ). 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 degrees C (POX I) and 10 degrees C (POX II), and POX I was more stable than POX II above 30 degrees C.
从荞麦种子中纯化出一个含过氧化物酶（POX）的组分。该POX由两种同工酶组成，即POX I和POX II，其纯化倍数分别为6.6倍和67.4倍。通过凝胶过滤法估计它们的分子量分别为46.1 kDa（POX I）和58.1 kDa（POX II）。虽然POX I和II都能氧化槲皮素、邻联茴香胺、抗坏血酸和愈创木酚，但只有POX II能氧化ABTS。动力学研究表明，POX I和II对槲皮素（0.071和0.028 mM）、ABTS（POX II为0.016 mM）和抗坏血酸（0.043和0.029 mM）的K(m)值低于对邻联茴香胺（0.229和0.137 mM）和愈创木酚（0.288和0）的K(m)值。除槲皮素外，POX I和II对各种底物的最适pH值几乎相同；POX I为pH 8.0，POX II为pH 4.5。它们的最适温度分别为30℃（POX I）和10℃（POX II），在30℃以上POX I比POX II更稳定。
