Laboratory of Chemistry and Function of Proteins and Peptides - LQFPP, Center for Biosciences and Biotechnology - CBB, State University of Northern Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, ZC, 28035-200 Campos dos Goytacazes, RJ, Brazil.
Laboratory of Cell and Tissue Biology - LBCT, Center for Biosciences and Biotechnology - CBB, State University of Northern Fluminense Darcy Ribeiro (UENF), Av. Alberto Lamego, 2000, ZC, 28035-200 Campos dos Goytacazes, RJ, Brazil.
Int J Biol Macromol. 2018 Jul 1;113:821-828. doi: 10.1016/j.ijbiomac.2018.03.024. Epub 2018 Mar 6.
Castor cake is a by-product of the extraction of oil from from seeds of castor plants (Ricinus communis). This by-product contains high levels of proteins, but a toxic protein, ricin, limits its use as an animal feed. Ricin can be efficiently inactivated by treatment with calcium oxide (CaO), which can be evaluated by a cytotoxicity assay using LLC-MK2 cells. The mechanism by which the CaO treatment inactivates ricin, however, is unclear. We report the structural changes responsible for ricin inactivation. Purified ricin was treated with 0.6% CaO and then analyzed by mass spectrometry. This treatment degraded the ricin at preferential sites. The aqueous CaO solution had a pH >12, which preferentially cleaved asparagine residues, followed by glutamine, serine and glycine residues. The alkaline pH affected the tertiary structure of the ricin, cleaving its polypeptide chains and thereby eliminating its cytotoxic activity.
蓖麻饼是从蓖麻（Ricinus communis）种子中提取油的副产品。这种副产品含有高水平的蛋白质，但一种有毒的蛋白质——蓖麻毒素限制了其作为动物饲料的使用。用氧化钙（CaO）处理可以有效地使蓖麻毒素失活，这可以通过使用 LLC-MK2 细胞的细胞毒性测定来评估。然而，CaO 处理使蓖麻毒素失活的机制尚不清楚。我们报告了导致蓖麻毒素失活的结构变化。用 0.6%的 CaO 处理纯化的蓖麻毒素，然后用质谱法进行分析。这种处理优先在特定部位降解蓖麻毒素。水性 CaO 溶液的 pH 值>12，优先切割天冬酰胺残基，其次是谷氨酰胺、丝氨酸和甘氨酸残基。碱性 pH 值影响蓖麻毒素的三级结构，切断其多肽链，从而消除其细胞毒性。
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