荔枝果皮过氧化酶的纯化与性质研究

荔枝果皮采后褐变是影响这一重要热带水果经济价值的主要问题,酚类物质的酶促氧化一直被认为是造成植物组织褐变的关键因素,其中多酚氧化酶被研究得最多.过氧化物酶在植物体中分布很广,能够氧化多种底物,在荔枝果皮中的含量也很高.非结合性过氧化物酶已经被证明在果实的采后成熟与老化过程中参与多种过程.在这项研究中,用磷酸缓冲液提取荔枝果皮的非结合性过氧化物酶,并通过硫酸铵沉淀,DEAFSephadex A-50离子交换柱层析以及Sephadex G-100凝胶过滤进行纯化.对得到的酶溶液进行了酶学性质的研究,发现荔枝果皮过氧化物酶具有较高的热稳定性和高的最适反应pH值(6.8),能够氧化许多底物尤其是单酚和各种多酚类物质,反应抑制剂专一性与其他植物来源的过氧化物酶略有不同显示了过氧化物酶参与荔枝果皮褐变过程的可能性,并为提高荔枝采后贮藏性提供了新的思路.

patrial characterization of soluble peroxidase in pericatp of litchi fruit

Soluble peroxidase in pericarp of litchi (Litchi chinensis sonn. Cv. Heiye) fruit was extracted by phosphate buffer and purified by annonium sulfate precipitation, ion exchange chromatography using DEAE Sephadex A-50column, and gel filtration using Sephadex G-100 column. The specific activity of the purified enzyme increased 65.70 fold over the crude extract with 45.66% recovery. The effects of pH and temperature on activity of peroxidase(POD) were assayed. The Km for H2O2 and 4-methylcatechol were detemined by Lineweaver Burk plots. Several compounds including phonelic compounds were used as the substrates of the enzyme for specificity study. The effects of various inhibitors on this peroxidsae were also assayed.