Department of Food Science and Engineering, College of Biological Sciences and Biotechnology, Beijing Key Laboratory of Forest Food Processing and Safety, Beijing Forestry University, Beijing 100083, China.
Agro-product Safety Research Center, Chinese Academy of Inspection and Quarantine, Beijing 100176, China.
Food Chem. 2021 May 15;344:128678. doi: 10.1016/j.foodchem.2020.128678. Epub 2020 Nov 20.
Purification of blueberry polyphenol oxidase (PPO) has not been substantially progressed for a long time, which leads to little further study. We purified three PPOs from blueberries for the first time by modified Native-Page. The PPO-2 consists of two subunits (68 and 36 kDa), whereas PPO-3 and PPO-4 contain only one subunit (36 kDa). The optimum pH and temperature of PPO-2, PPO-3, and PPO-4 were 5.8-6.2 and 40 °C-45 °C with catechol as a substrate. The optimal substrates for them were all catechol (K = 14.91, 7.19, and 11.20, respectively). High-pressure processing (HPP) had a limited inhibitory effect on the three PPOs. The activities of PPO-2, PPO-3, and PPO-4 were significantly reduced with increased SDS concentration. The binding of substrate to catalytic cavity is related to the residues His76, His209, His213, Gly228, and Phe230. The carbonyl group of residue Gly228 is one of the key sites for screening substrates.
蓝莓多酚氧化酶（PPO）的纯化长期以来没有取得实质性进展，这导致对其进一步的研究很少。我们首次通过改良的 Native-Page 从蓝莓中纯化了三种 PPO。PPO-2 由两个亚基（68 和 36 kDa）组成，而 PPO-3 和 PPO-4 仅含有一个亚基（36 kDa）。PPO-2、PPO-3 和 PPO-4 的最适 pH 和温度分别为 5.8-6.2 和 40°C-45°C，以儿茶酚为底物。它们的最佳底物均为儿茶酚（K 值分别为 14.91、7.19 和 11.20）。高压处理（HPP）对三种 PPO 的抑制作用有限。随着 SDS 浓度的增加，PPO-2、PPO-3 和 PPO-4 的活性显著降低。底物与催化腔的结合与残基 His76、His209、His213、Gly228 和 Phe230 有关。残基 Gly228 的羰基是筛选底物的关键位点之一。
