Antioxidant activity of cysteine, tryptophan, and methionine residues in continuous phase β-lactoglobulin in oil-in-water emulsions
Antioxidant activity of cysteine, tryptophan, and methionine residues in continuous phase β-lactoglobulin in oil-in-water emulsions
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DOI：
10.1021/jf0521698
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发表时间：
2005-12-28
影响因子：
6.1
通讯作者：
Decker, EA
中科院分区：
文献类型：
--
作者：
Elias, RJ;McClements, DJ;Decker, EA
分散在水包油乳状液连续相中的蛋白质能够抑制脂质氧化反应。这些蛋白质的抗氧化活性被认为既包括氨基酸残基对自由基的清除作用，也包括对氧化前过渡金属的螯合作用；然而，发生这种情况的确切机制尚不清楚。在这项研究中，测定了半胱氨酸、色氨酸和蛋氨酸残基在Brij稳定的曼哈登水包油乳剂中连续相β-乳球蛋白(β-LG)中的氧化稳定性。通过脂质过氧化氢和硫代巴比妥酸活性物质分析表明，低浓度连续相β-LG(250和750mUg/mL)的存在显著抑制了脂质氧化。在β-LG中观察到半胱氨酸在色氨酸之前氧化，两个残基都在脂肪氧化之前被氧化。尽管β-LG的氧化敏感性很高，但没有观察到蛋氨酸残基被氧化。可以想象，氨基酸残基的表面暴露极大地影响了它们的氧化动力学，这可能解释了为什么某些残基相对于其他残基优先被氧化。进一步阐明氨基酸清除自由基的机制可能导致蛋白质作为抗氧化剂在水包油食品乳状液中更有效地应用。
Proteins dispersed in the continuous phase of oil-in-water emulsions are capable of inhibiting lipid oxidation reactions. The antioxidant activity of these proteins is thought to encompass both free radical scavenging by amino acid residues and chelation of prooxidative transition metals; however, the precise mechanism by which this occurs remains unclear. In this study, the oxidative stability of cysteine, tryptophan, and methionine residues in continuous phase beta-lactoglobulin (beta-Lg) in a Brij-stabilized menhaden oil-in-water emulsion was determined. The presence of low concentrations of continuous phase beta-Lg (250 and 750 mu g/mL) significantly inhibited lipid oxidation as determined by lipid hydroperoxides and thiobarbituric acid reactive substances analysis. It was observed that cysteine oxidized before tryptophan in beta-Lg, and both residues oxidized before lipid oxidation could be detected. No oxidation of the methionine residues of beta-Lg was observed despite its reported high oxidative susceptibility. It is conceivable that surface exposure of amino acid residues greatly affects their oxidation kinetics, which may explain why some residues are preferentially oxidized relative to others. Further elucidation of the mechanisms governing free radical scavenging of amino acids could lead to more effective applications of proteins as antioxidants within oil-in-water food emulsions.