采用十二烷基硫酸钠-聚丙烯酰胺凝胶电泳(SDS-PAGE)和免疫印迹(Western blot)方法,通过体外模拟消化实验分析水产品主要过敏原原肌球蛋白(Tropomyosin,TM)和小清蛋白(Parvalbumin,PV)的消化特性,主要研究酶/蛋白的比值、pH值对模拟胃液(SGF)消化过敏蛋白稳定性的影响。结果表明,提高胃蛋白酶的相对量使甲壳类水产品TM从消化稳定性转变成消化不稳定性,但是TM具有较强的消化稳定性,当酶/蛋白比值提高到10/1时,一些稳定的降解条带仍未被完全分解;当pH≥5时胃液消化会受到抑制,甲壳类水产品TM和鱼类PV均不会被消化分解。在优化条件(0.33U酶/μg蛋白,pH3.5)的SGF消化试验中,甲壳类水产品TM具有较高的消化稳定性,而鱼类PV能被较快分解;甲壳类水产品过敏蛋白相对于非过敏蛋白具有较高的消化稳定性,其降解产物仍可能引起过敏反应的发生。
Stability in simulated gastric fluid (SGF) is regarded as an important parameter in estimation of food allergenicity. The digestive conditions of crustacean allergens (tropomyosin, TM), fish allergens (parvalbumin, PV) and nonal- lergenic proteins from muscles of mud crab (Scylla serrata), Chinese mitten crab (Eriocheir sinensis), grass prawn (Penaeus monodon), whiteleg shrimp (Penaeus vannamei), Crucian carp (Carassius auratus cuvieri) and Silver carp (Hypophthalmichthys molitrix) in SGF were compared. Porcine pepsin was used to simulate digestive proteinases from human. Stabilities of allergens were studied with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western-blot at different pepsin/protein ratios and pH. It was found that the apparent susceptibility of allergens to proteolysis was dependent on the ratio of pepsin to allergen. TM was of relatively higher stability; even at pepsin/allergen = 10/t, some stable degradation fragments still existed. Under optimized conditions (0.33U pepsin/μg protein, pH 3.5), crustacean allergen TM was relatively resistant to pepsin, but fish allergen PV was rapidly degraded within a short period of time. Further study by Western-blot using sera from crustacean-allergic patients indicated that allergenicity of TM was partially decreased, but the products of TM digested by pepsin still had a little IgE-binding capacity.