Cao Xinyuan, Liang Jingbang, Aluko Rotimi E, Thiyam-Holländer Usha
Department of Food and Human Nutritional Sciences, University of Manitoba, Winnipeg, Canada.
School of Food Science and Technology, Jiangnan University, Wuxi, China.
J Food Biochem. 2019 Jun;43(6):e12884. doi: 10.1111/jfbc.12884. Epub 2019 May 6.
The enzymatic oxidation of sinapic acid catalyzed by horseradish peroxidase (HRP) or tyrosinase was investigated using model systems, which contained the pure compound or canola meal. Spectrophotometric scanning of pure sinapic acid solution in the presence of HRP (0.2 U) or tyrosinase (40.3 U) showed continuous decreases in absorbance at 304 nm over a period of 90 and 60 min, respectively. HPLC analyses of enzymatic end products, obtained by the catalysis with HRP or tyrosinase, indicated the presence of two main compounds (1 and 2). After alkaline hydrolysis of canola meal, sinapic acid that was released from sinapine was also converted to compounds 1 and 2 by HRP or tyrosinase. Enzyme reaction kinetics results indicate that the catalytic efficiency (CE = 0.538), reaction velocity (V = 5.67 ∆A/h), and Michaelis-Menten constant (K = 926.64 µM) of HRP are significantly higher than those of tyrosinase (CE = 0.041, V = 0.41 ∆A/h, K = 173.03 µM) at 50-250 μM pure sinapic acid concentrations. PRACTICAL APPLICATIONS: Canola meal contains a large amount of sinapine, which is the choline ester of sinapic acid, a strong antioxidant compound. However, the oxidation or decarboxylation products of sinapic acid could add value by increasing the level of electron-dense carboxylic and carbonyl compounds. In this study, enzymatic treatment of alkaline-hydrolyzed canola meal with horseradish peroxidase (HRP) and tyrosinase was investigated and shown to be suitable for converting sinapic acid into oxidized compounds. Therefore, the enzymatic treatment is a potential application for value-added processing of canola meal.
使用包含纯化合物或油菜籽粕的模型系统，研究了辣根过氧化物酶（HRP）或酪氨酸酶催化的芥子酸酶促氧化反应。在HRP（0.2 U）或酪氨酸酶（40.3 U）存在的情况下，对纯芥子酸溶液进行分光光度扫描，结果显示在90分钟和60分钟内，304 nm处的吸光度分别持续下降。对HRP或酪氨酸酶催化得到的酶促终产物进行HPLC分析，结果表明存在两种主要化合物（1和2）。油菜籽粕经碱性水解后，从芥子碱中释放出的芥子酸也会被HRP或酪氨酸酶转化为化合物1和2。酶反应动力学结果表明，在50 - 250 μM的纯芥子酸浓度下，HRP的催化效率（CE = 0.538）、反应速度（V = 5.67 ∆A/h）和米氏常数（K = 926.64 μM）显著高于酪氨酸酶（CE = 0.041，V = 0.41 ∆A/h，K = 173.03 μM）。实际应用：油菜籽粕含有大量芥子碱，它是强抗氧化化合物芥子酸的胆碱酯。然而，芥子酸的氧化或脱羧产物可以通过增加电子密度高的羧基和羰基化合物的含量来增加价值。在本研究中，对用辣根过氧化物酶（HRP）和酪氨酸酶对碱性水解的油菜籽粕进行酶处理进行了研究，结果表明该处理适合将芥子酸转化为氧化产物。因此，酶处理是油菜籽粕增值加工的一种潜在应用。
