Inborn errors of amino acid metabolism, such as phenylketonuria (PKU), are human genetic conditions that result in an inability to metabolize certain amino acids, requiring lifelong maintenance of a very restrictive low-protein diet. In the case of PKU, this diet does not permit consumption of most maize (Zea mays L.) products, yet maize is a major part of the human diet and is especially significant in some cultures. Kernel protein content, and to a lesser extent amino acid composition, is variable in maize. Breeding maize for low kernel protein content or low amounts of specific amino acids such as phenylalanine might expand the restrictive diets and improve quality of life for people with amino acid metabolic disorders. To test the potential of breeding low-protein-content maize, diverse samples of hybrid or open-pollinated cultivars and inbreds were evaluated across two locations in two years for grain protein content and amino acid composition. Consistent with previous reports, kernel protein content varied widely across maize varieties and is highly heritable in the broad sense. We found that phenylalanine content (as a proportion of grain weight) and phenylalanine composition (as a proportion of total protein) are also highly heritable in the broad sense. As previously reported, reasonably accurate estimation of protein content is possible with near-infrared spectrophotometry, whereas measuring phenylalanine content requires a destructive, costly, and time-consuming laboratory analysis. Because phenylalanine content was strongly correlated with total kernel protein, breeding primarily aimed at reducing grain protein content should permit efficient selection of maize cultivars sufficiently low in phenylalanine to permit broader inclusion in the PKU diet.

中文翻译：

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为限制蛋白质的饮食培育低蛋白质玉米的潜力

氨基酸代谢的先天性错误，例如苯丙酮尿症 (PKU)，是导致某些氨基酸无法代谢的人类遗传病，需要终生维持非常严格的低蛋白饮食。在 PKU 的情况下，这种饮食不允许食用大多数玉米（Zea maysL.) 产品，但玉米是人类饮食的主要部分，在某些文化中尤其重要。玉米的籽粒蛋白质含量和氨基酸组成在较小程度上是可变的。培育低谷粒蛋白质含量或低含量特定氨基酸（如苯丙氨酸）的玉米可能会扩大限制性饮食并改善氨基酸代谢紊乱患者的生活质量。为了测试培育低蛋白质含量玉米的潜力，两年内在两个地点评估了杂交或开放授粉品种和近交品种的不同样品的谷物蛋白质含量和氨基酸组成。与之前的报道一致，不同玉米品种的籽粒蛋白质含量差异很大，并且在广义上具有高度遗传性。我们发现苯丙氨酸含量（占粒重的比例）和苯丙氨酸组成（占总蛋白质的比例）在广义上也是高度遗传的。正如之前报道的那样，使用近红外分光光度法可以合理准确地估计蛋白质含量，而测量苯丙氨酸含量需要破坏性、昂贵且耗时的实验室分析。由于苯丙氨酸含量与总籽粒蛋白质密切相关，主要旨在降低谷物蛋白质含量的育种应允许有效选择苯丙氨酸含量足够低的玉米品种，以允许更广泛地纳入 PKU 饮食。使用近红外分光光度法可以合理准确地估计蛋白质含量，而测量苯丙氨酸含量需要破坏性、昂贵且耗时的实验室分析。由于苯丙氨酸含量与总籽粒蛋白质密切相关，主要旨在降低谷物蛋白质含量的育种应允许有效选择苯丙氨酸含量足够低的玉米品种，以允许更广泛地纳入 PKU 饮食。使用近红外分光光度法可以合理准确地估计蛋白质含量，而测量苯丙氨酸含量需要破坏性、昂贵且耗时的实验室分析。由于苯丙氨酸含量与总籽粒蛋白质密切相关，主要旨在降低谷物蛋白质含量的育种应允许有效选择苯丙氨酸含量足够低的玉米品种，以允许更广泛地纳入 PKU 饮食。