花生致敏原Ara h 1的重组表达与纯化

Ara h 1是花生中含量最高的过敏原,也是致敏性较高的蛋白之一。目前提纯Ara h 1的方法大多涉及2至3步柱层析,步骤繁琐且成本较高。本文中,将带有6×his标签的Ara h 1基因与pET-32a表达载体融合,构建重组质粒并转化大肠杆菌BL21(DE3)pLysS,诱导使其表达目标蛋白。菌体裂解后使用Ni-NTA吸附、梯度洗脱对Ara h 1进行纯化。采用质谱及Western-blot鉴定纯化蛋白的种类及免疫活性。结果显示,质粒中目标基因的序列与NCBI数据库中Ara h 1的基因数据相符;300 mmol/L异丙基-β-D-硫代吡喃半乳糖苷22℃诱导菌液22 h时蛋白表达量最高;添加15 mmol/L十二烷基磺酸钠可将蛋白释放到上清液中,使用含50,100 mmol/L咪唑的洗脱液分别洗脱2次和1次后得到纯度较高且免疫原性良好的重组Ara h 1。

花生致敏蛋白Ara h 1的电子克隆及生物信息学分析

花生致敏已成为重要的食品安全问题,花生蛋白中含有的Ara h 1是重要的致敏蛋白。运用生物信息学的电子克隆方法得到Shanyou523、Luhua14、USDA-Tifton三个花生品种的Ara h 1基因,并进行序列特征分析、多序列比对和结构域分析,探讨蛋白质水平的氨基酸差异与其致敏性的关系。

质谱法分析烘焙对花生过敏原Ara h 1潜在致敏性的影响

为研究烘焙对花生过敏原Ara h 1潜在致敏性的影响,采用高离液序列盐溶液从鲜花生和烘焙花生中提取总蛋白,通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析烘焙前后蛋白条带变化情况,并对其中的花生主要过敏蛋白Ara h 1条带进行质谱和Swiss-Model模型分析。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳结果显示,烘焙花生蛋白出现了大分子聚合物条带以及较多弥散状蛋白条带,说明烘焙过程中蛋白质会发生聚集,同时也可能发生降解。对鲜花生Ara h 1条带的质谱分析结果显示,检测出70条肽段,覆盖率达到79.2%;而烘焙后其中40条肽段未能检出,但新增1条肽段,且覆盖率降至43.9%。全部71个肽段涉及到Ara h 1的18个过敏原线性表位,酶解后鲜花生中检出16个过敏原线性表位被破坏,烘焙花生中仅发现12个被破坏。结论:烘焙加工会破坏蛋白质高级结构,掩盖了部分酶切位点,减少了酶解对过敏原线性表位的破坏,这可能是导致烘焙加工后Ara h 1致敏性强于未加工样品的原因。

花生过敏原Ara h 1蛋白的原核表达及致敏性分析

从花生中提取总RNA,用反转录聚合酶链式反应得到花生过敏原Ara h 1基因,构建pET-28a-Ara h 1表达载体,转入Rosetta(DE3)宿主表达菌中诱导产物表达,用镍离子亲和层析法纯化得到目的蛋白。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳结果显示目的蛋白分子质量约为75 kDa,与预计相符;经质谱鉴定为Ara h 1蛋白。用BALB/c小鼠模型评价重组Ara h 1蛋白的致敏性结果显示,重组Ara h 1蛋白致敏小鼠血清中特异性抗体、Th2型细胞因子、组胺含量升高,空肠和肺组织发生病变,表明重组Ara h 1蛋白可以导致小鼠发生Th2型过敏反应,且有与天然Ara h 1蛋白相似的致敏性。同时RBL细胞模型结果显示重组Ara h 1蛋白还可导致RBL细胞脱颗粒,释放β-己糖苷酶,进一步表明重组Ara h 1蛋白具有致敏性。

Peanut Allergens Attached with p-Aminobenzamidine Are More Resistant to Digestion than Native Allergens

Despite being known as resistant proteins, peanut allergens (Ara h 1 and Ara h 2) can be digested and cause allergic reactions. Making the allergens more resistant to digestion may aid in non-absorption and excretion of the allergens. Our objectives were to make Ara h 1 and Ara h 2 more resistant to digestion and test them in a model system using trypsin as the digestive enzyme. The resistant allergens were prepared by covalently attaching p-aminobenzamidine (pABA), a protease inhibitor, to peanut allergens in an extract or on a PVDF membrane using glutaraldehyde, and were then tested for resistance to trypsin digestion. SDS-PAGE and Western blot were performed to determine the allergenic capacity of the modified allergens. A control was prepared using glycine instead. Results showed that Ara h 2, when covalently attached with pABA, was more resistant to trypin digestion than the native allergen. Similarly, Ara h 1, prepared on a PVDF membrane and treated with pABA, displayed a resistance to trypsin digestion. Treatment of the allergens with glycine (a control) instead of pABA showed that the modified allergens were as digestible as native allergens. Blot assays showed that the pABA-treated allergens exhibited a lower allergenic capacity than native allergens. It was concluded that pABA, when attached to peanut allergen Ara h 1 or Ara h 2, inhibited digestion of the allergen by trypsin and reduced their allergenic capacity as well.

花生过敏原结构及加工研究进展

花生过敏已成为世界各地普遍存在的公众性健康问题,得到广泛关注,对花生过敏原的研究日渐深入。过敏原结构为加工降低其过敏原性提供基础,用各种加工手段降低甚至消除花生过敏原蛋白的致敏性,尤其是Ara h 1、Ara h 2和Ara h 6、Ara h 3/4这些含量高、致敏性强的主要过敏原的致敏性已备受重视。本文主要介绍花生过敏原研究在结构及加工方面的进展,以期为低致敏甚至脱敏花生的生产提供一定的参考,以保证实现丰富食物过敏患者食品选择的同时,有效降低食品安全风险。

含扩增内标的花生过敏原PCR检测方法

基于花生主要过敏原Ara h 1的基因序列设计引物,采用复合引物技术构建竞争性扩增内标,以157copies/PCR为内标添加量,建立含扩增内标的花生过敏原PCR检测方法。结果表明,该方法的检测灵敏度为0.1ng DNA,特异性良好;将该方法应用于9种食品的花生过敏原成分检测,结果与标签标识一致,表明该方法具有一定的应用价值。