酪蛋白水解物的Plastein反应修饰及ACE抑制活性变化

Modification of casein hydrolysates by plastein reaction and ACE inhibitory activity of the modified products

采用中性蛋白酶水解酪蛋白,一定条件下制备水解度为13.0%、IC50质量浓度为40.4 mg/L的酪蛋白水解物。利用中性蛋白酶对所制备出的水解物进行plastein反应修饰,以反应体系的游离氨基量的变化为评价指标,通过单一因素试验研究酶添加量、底物质量分数、反应时间和反应温度对修饰反应的影响。结果表明,适宜的反应条件为中性蛋白酶添加量3 kU/g蛋白质、底物质量分数60%、反应时间6 h、反应温度20℃。制备5个不同反应程度的修饰产物,ACE抑制活性分析结果显示,修饰产物的IC50降至14.7~31.1 mg/L,表明中性蛋白酶催化的plastein反应修饰提高酪蛋白水解物的ACE抑制活性,且ACE抑制活性的提高程度与plastein反应程度有关。

Casein was hydrolyzed by Neutrase under the fixed conditions to prepare casein hydrolysates that had the degree of hydrolysis of 13.0 % and value of IC50 about 40.4 μg/mL.The obtained hydrolysates then were modified by plastein reaction catalyzed by Neutrase.The effects of the addition level of Neutrase,the concentration of casein hydrolysates,reaction time and temperature on the plastein reaction of casein hydrolysates were studied by single factor experiments,with the decreased amount of free amino groups of the hydrolysates as the evaluation index.The results indicated that the suitable reaction conditions were addition level of Neutrase of 3 ku/g proteins,substrate concentration of 60%,reaction time of 6 h and reaction temperature of 20 ℃.Five modified casein hydrolysates were prepared with the selected reaction conditions but different reaction times.The analysis results showed that the modified hydrolysates had an improved ACE-inhibitory activity because their values of IC50 ranged from 14.7 to 31.1μg/mL.Our results indicated that Neutrase-catalyzed plastein reaction could be applied to enhance the ACE-inhibitory activity of casein hydrolysates,and reaction extent of plastein reaction showed impact on the ACE-inhibitory activity of the modified product.