Department of Food Science, University of Pretoria, Private Bag X20, Hatfield 0028, South Africa.
J Agric Food Chem. 2011 Sep 14;59(17):9265-70. doi: 10.1021/jf201878p. Epub 2011 Aug 16.
Transgenic sorghum (TG) lines with altered kafirin synthesis, particularly suppression of γ-kafirin synthesis, and improved protein quality have been developed. The proportion of kafirin extracted with 60% tert-butyl alcohol alone was greatly increased in the TG lines. However, the total amount of kafirin remained unchanged. Further, in the TG lines, the kafirin was much less polymerized by disulfide bonding. There was also evidence of compensatory synthesis of other kafirin proteins. Cooked protein digestibility was increased in the TG form, even after removal of interfering starch. The TG protein bodies were intermediate in appearance between the normal type and the invaginated high digestibility mutants. Hence, the increased protein digestibility of these TG lines is probably related to their lower levels of disulfide-bonded kafirin polymerization, allowing better access of proteases. This work appears to confirm that disulfide bond formation in kafirin is responsible for the reduced protein digestibility of cooked sorghum.
已培育出改变了角蛋白合成的转基因高粱（TG）系，特别是抑制γ-角蛋白合成和提高蛋白质质量。单独用 60%叔丁醇提取的角蛋白比例在 TG 系中大大增加。然而，角蛋白的总量保持不变。此外，在 TG 系中，角蛋白通过二硫键的聚合作用大大减少。也有其他角蛋白蛋白补偿合成的证据。即使去除了干扰淀粉，TG 形式的蒸煮蛋白消化率也增加了。TG 蛋白体在外观上介于正常型和内陷型高消化率突变体之间。因此，这些 TG 系的蛋白质消化率增加可能与其二硫键结合的角蛋白聚合程度较低有关，这使得蛋白酶更容易进入。这项工作似乎证实了角蛋白中二硫键的形成是导致蒸煮高粱蛋白质消化率降低的原因。
