香菜叶多酚氧化酶的分离纯化与部分酶学性质研究

新鲜香菜叶经匀浆、缓冲液提取、硫酸铵分级沉淀、DEAE-Sepharose离子交换层析、Superdex-200凝胶过滤层析，获得电泳纯的多酚氧化酶。该酶比活力达到5 622.95 U/mg，酶活回收率为3.90%，纯化倍数为126.08；全酶分子质量为111.10 kD，亚基分子质量为55.60 kD；最适温度为37 ℃，最适pH值为6.5；在25～45 ℃及pH 6.0～7.0范围内有较好的稳定性；在最适条件下测得其Km值为4.04×10－2 mol/L；甲醇、乙醇、异丙醇、氯仿及柠檬酸、抗坏血酸、Ca2＋、Hg2＋、Ba2＋对其有抑制作用，Co2＋、Pb2＋对其具有一定的激活作用。

Isolation,Purification and Enzymatic Characterization of Polyphenol Oxidase from Coriander Leaves

Electrophoretically pure polyphenol oxidase (PPO) from fresh coriander leaves was obtained through
homogenization, buffer solution extraction, ammonium sulfate precipitation, DEAE-Sepharose ion exchange chromatography
and Superdex-200 gel filtration chromatography. The specific activity of purified PPO was 5 622.95 U/mg with a recovery of
3.90% and a purification factor of 126.08. The molecular weights of this enzyme and its subunits were 111.10 and 55.60 kD,
respectively. It was relatively stable in the range of 25–45 ℃ and pH 6.0–7.0. Its optimum temperature and pH were 37 ℃
and 6.5, respectively. Furthermore, its Km was 4.04 × 10-2 mol/L under the optimum conditions. Its activity was inhibited by
methanol, ethanol, isopropanol, trichloromethan, citric acid and ascorbic acid as well as some metal ions such as Ca2+, Hg2+
and Ba2+, but was activated by Co2+ and Pb2+.