利用谷氨酰胺酶(EC 3.5.1.2)对酪蛋白进行限制性脱酰胺和水解处理,以SDS-PAGE及排阻色谱分析评价产物的蛋白质降解情况,并制备具有较低脱酰胺度的脱酰胺酪蛋白产物。在酪蛋白质量浓度为5%、谷氨酰胺酶添加量400 U/kg酪蛋白、37℃的条件下分别反应6 h、12 h和24 h,制得脱酰胺度分别为2.8%、5.8%和8.5%,水解度分别为2.5%、3.4%和4.9%的脱酰胺酪蛋白。评价这3种脱酰胺酪蛋白产物对Fe2+和Ca2+的螯合能力,结果表明,脱酰胺酪蛋白产物对Fe2+和Ca2+的螯合能力高于酪蛋白,并随着脱酰胺度的增加而提高。

Glutaminase(EC 3.5.1.2) was applied in the present work to treat casein for deamidation and hydrolysis to a limited reaction extent.SDS-PAGE and size exclusion chromatography analysis were used to evaluate the degradation of casein.Some deamidated casein products with lower degree of deamidation were prepared with reaction conditions of casein concentration of 5 %(w/v),glutaminase addition level of 400 U/kg casein,reaction temperature of 37 ℃ and reaction time were 6,12 and 24 h,respectively.Three deamidated casein products prepared had the degree of deamidation of 2.8%,5.8% and 8.5 %,or degree of hydrolysis of 2.5%,3.4% and 4.9 %,respectively,were prepared.The iron or calcium(Ⅱ) chelating activities of three deamidated caseind products were analyzed.The results indicated that the iron or calcium(Ⅱ) chelating activities of three deamidated casein products were higher than that of casein,and would be enhanced as degree of deamidation increased.