变性对转谷氨酰胺酶在乳蛋白间交联影响初探

Effect of denaturation on cross-linking of milk protein with transglutaminase

利用SDS-PAGE电泳结合凝胶成像分析技术,比较了在非变性、加入还原剂变性和加热后再加入还原剂变性三种条件下转谷氨酰胺酶对酪蛋白和乳清蛋白之间的交联情况。结果表明:在非变性条件下,酪蛋白质量分数下降96%,乳清蛋白下降15%,酪蛋白和乳清蛋白几乎不能交联,超分子量聚合物是酪蛋白单一聚合物,α乳白蛋白形成部分低聚体;在加入还原剂时,酪蛋白质量分数下降86%,乳清蛋白下降30%,反应4h后有少量乳清蛋白和酪蛋白中某一组分交联;预热更有助于酪蛋白和乳清蛋白聚合,在第三种条件下,反应24h后乳清蛋白下降60%。

The cross-linking of sodium caseinate and whey protein isolate （WPI） at three different conditions using transglutaminase （Tgase） was studied. The extent of polymerization was detemined SDS-PAGE associated with gel image analysis. It showed： （a） it is impossble for the cross-linking between sodium caseinate and whey protein isolate at the native condition by Tgase because of different spatial structures, α-LA produce some monopolymers. （b）30% whey protein isolate and 86% caseinate were polymerized by Tgase with addition of 20 mmol/L DTT,. β-LG produce monopolymers after 8 h. （c） Preheating facilitated the cross-linking between caseinate and whey protein isolate , for we found that 24 h later 60% WPI and 74% CN were reduced simultaneously with addition of 20 mmol/L DTT after preheated. 80 ℃ 20 min.