Baxter Jeffrey H, Lai Chron-Si, Phillips Rosalyn R, Dowlati Lobat, Chio Julie J, Luebbers Steven T, Dimler Steven R, Johns Paul W
Ross Products Division, Abbott Laboratories, 3300 Stelzer Road, Columbus, OH 43219, USA.
J Chromatogr A. 2007 Jul 20;1157(1-2):10-6. doi: 10.1016/j.chroma.2007.04.035. Epub 2007 Apr 20.
A direct and simultaneous HPLC/UV determination of methionine and methionine sulfoxide in enzyme-hydrolyzed milk proteins is described. Protein hydrolysis is accomplished by a three-enzyme (pronase, leucine aminopeptidase, prolidase) 20-h/37 degrees C digestion. A gradient elution reversed-phase HPLC system with UV detection at 214 nm and 280 nm is then used to determine the quantitative releases of methionine sulfoxide, methionine, tyrosine, and tryptophan. The ease of methionine oxidation by a wide variety of oxidants, coupled with the quantitative release of both methionine and its sulfoxide by the three-enzyme hydrolysis, renders the approach valuable for identifying oxidized milk proteins. The relatively simple method proved accurate and precise in its application to commercial milk products, finding methionine sulfoxide levels as high as 74% of the total methionine.
本文描述了一种直接同时测定酶水解乳蛋白中蛋氨酸和蛋氨酸亚砜的高效液相色谱/紫外检测法。蛋白质水解通过三种酶（链霉蛋白酶、亮氨酸氨肽酶、脯氨酰肽酶）在37℃下消化20小时来完成。然后使用在214nm和280nm处进行紫外检测的梯度洗脱反相高效液相色谱系统，来测定蛋氨酸亚砜、蛋氨酸、酪氨酸和色氨酸的定量释放。多种氧化剂容易使蛋氨酸氧化，再加上三种酶水解能定量释放蛋氨酸及其亚砜，使得该方法对于鉴定氧化乳蛋白很有价值。这种相对简单的方法在应用于商业乳制品时被证明准确且精密，发现蛋氨酸亚砜水平高达总蛋氨酸的74%。
