酵母源金属硫蛋白在模拟胃肠环境中对铅离子的螯合作用

Lead ion-chelating function of metallothioneins from yeast origin in mimic gastrointestinal environment

目的探讨酵母源金属硫蛋白(metallothionein,MT)在模拟胃肠环境中对铅离子的螯合作用,为酵母源MT促排铅功能的深入研究及相关促排铅产品的开发提供一定的理论参考与数据支持。方法以动物源金属硫蛋白(ZnMT)为对照,采用石墨炉原子吸收光谱法测定2种构型酵母源金属硫蛋白(MT-Ⅰ、MT-Ⅱ)在模拟胃肠环境中对铅离子的螯合作用,计算MT对铅离子螯合率,并分析螯合体系重金属离子的迁移与转化情况及酵母源MT在模拟胃肠环境中的稳定性。结果 MT在模拟胃肠环境中表现出显著的螯合铅离子能力,并呈现量效关系。在模拟胃环境中,MT-Ⅰ与MT-Ⅱ对铅离子的螯合率显著高于Zn-MT(P<0.05);胃蛋白酶对MT-Ⅰ和Zn-MT螯合铅离子效果具有一定的减弱作用(P<0.05),而对MT-Ⅱ影响不明显(P>0.05)。在模拟肠环境中,3种MT对铅离子的螯合效果差异有统计学意义(P<0.05),其螯合能力为Zn-MT>MT-Ⅰ>MT-Ⅱ,且显著高于同浓度MT在模拟胃环境中对铅离子的螯合率(P<0.05);胰蛋白酶对MT螯合铅离子效果影响较小(P>0.05)。MT在螯合铅离子过程中,可同时释放自身结合重金属元素,且自身重金属离子释放率显著高于铅离子螯合率(P<0.05);2种构型的酵母源MT在模拟肠环境中降解程度较弱,稳定性较好。结论 MT-Ⅰ与MT-Ⅱ在模拟胃肠环境中均能显著地螯合铅离子,并在12 h内能较好地抵抗模拟胃肠环境的消化,保持其螯合铅离子能力。

Objective To investigate the lead ion-chelating function of metallothioneins（MTs）from yeast origin in mimic gastrointestinal environment and provide theoretical reference and data support for the further study on promoting effect of MTs from yeast origin on lead excretion as well as development of relevant products. Methods The lead ion-chelating effects of MTs of two configurations from yeast origin, MT-Ⅰand MT-Ⅱ, in mimic gastrointestinal environment were determined by graphite furnace atomic absorption spectroscopy, using Zn-MT, a metallothionein from animal origin, as control,based on which the chelation rate of lead ion by MT was calculated, the migration and transformation of heavy metal ions in the chelation system, as well as the stability of MTs from yeast origin in mimic gastrointestinal environment, were ana-lyzed. Results MTs showed significantly dose-dependent lead ion-chelating ability in mimic gastrointestinal environment.In mimic gastric juice, the chelation rates of lead ion by MT-Ⅰand MT-Ⅱwere significantly higher than that by Zn-MT（P 〈 0. 05）. Pepsin weakened the lead ion-chelating abilities of MT-Ⅰand Zn-MT at a certain degree（P 〈 0. 05）, while showed no significant effect on MT-Ⅱ（P 〉 0. 05）. In mimic intestinal juice, the lead ion-chelating abilities of three MTs showed significant difference（P 〈 0. 05）. In the turn of chelating abilities, the MTs were Zn-MT, MT-Ⅰ and MT-Ⅱ,which were significantly higher than those at the same concentration in mimic gastric juice（P 〈 0. 05）. Trypsin showed little effect on the leading ion-chelating abilities of MTs（P 〉 0. 05）. During chelation, the MTs released the bound heavy metal ions, of which the release rates were significantly higher than the chelation rate of lead ion（P 〈 0. 05）. Both the degradation levels of MT-Ⅰand MT-Ⅱ were relatively low in mimic intestinal juice, indicating high stabilities. Conclusion MT-Ⅰand MT-Ⅱ from yeast origins chelated lead ion significantly in mimic gastrointestinal environment, and resisted the digestion within 12 h to maintain their chelating abilities.