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Abstract：
Soybeans are an excellent source of protein in monogastric diets and rations with ∼75% of soybeans produced worldwide used primarily for animal feed. Even though soybeans are protein-rich and have a well-balanced amino acid profile, the nutritive quality of this important crop could be further improved by elevating the concentrations of certain amino acids. The levels of the sulfur-containing amino acids cysteine and methionine in soybean seed proteins are inadequate for optimal growth and development of monogastric animals, which necessitates dietary supplementation. Subsequently, concerted efforts have been made to increase the concentrations of cysteine and methionine in soybean seeds by both classical breeding and genetic engineering; however, these efforts have met with only limited success. In this review, we discuss the strengths and weakness of different approaches in elevating the sulfur amino acid content of soybeans. Manipulation of enzymes involved in the sulfur assimilatory pathway appears to be a viable avenue for improving sulfur amino acid content. This approach requires a through biochemical characterization of sulfur assimilatory enzymes in soybean seeds. We highlight recent studies targeting key sulfur assimilatory enzymes and the manipulation of sulfur metabolism in transgenic soybeans to improve the nutritive value of soybean proteins.
摘要：
大豆是单胃饮食和口粮中蛋白质的极好来源，全球生产的大豆中有75％主要用于动物饲料。尽管大豆富含蛋白质，氨基酸分布平衡良好，这种重要作物的营养品质可以通过提高某些氨基酸的浓度来进一步提高。大豆种子蛋白中含硫氨基酸半胱氨酸和蛋氨酸的水平不足以促进单胃动物的最佳生长和发育。这就需要饮食补充。随后，通过经典育种和基因工程，已经做出了共同努力来增加大豆种子中半胱氨酸和蛋氨酸的浓度；但是，这些努力只取得了有限的成功。在这次审查中,我们讨论了提高大豆中硫氨基酸含量的不同方法的优缺点。操纵参与硫同化途径的酶似乎是提高硫氨基酸含量的可行途径。这种方法需要通过生化表征大豆种子中的硫同化酶。我们重点介绍了针对关键硫同化酶的最新研究以及对转基因大豆中硫代谢的操纵，以提高大豆蛋白的营养价值。
