Sparing of methionine requirements: Evaluation of human data takes sulfur amino acids beyond protein
Sparing of methionine requirements: Evaluation of human data takes sulfur amino acids beyond protein
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DOI：
10.1093/jn/136.6.1676s
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发表时间：
2006-06-01
影响因子：
4.2
通讯作者：
Fukagawa, Naomi K.
中科院分区：
文献类型：
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作者：
Fukagawa, Naomi K.
氨基酸与蛋白质和氮需要量之间的密切关系是众所周知的。营养学研究的重点是食物满足氮和必需氨基酸（IAA）需求的能力，并得出结论，蛋白质的质量而不仅仅是数量至关重要。这对于含硫氨基酸（SAA）甲硫氨酸和半胱氨酸尤其相关，因为对它们与慢性疾病（例如，心血管疾病、痴呆、肝硬化）、免疫调节、DNA转录和RNA翻译。已经花费了相当大的努力来确定半胱氨酸是否以及在多大程度上可以节省对IAA甲硫氨酸的需求。人体体内研究通常一致认为SAA的饮食需求范围为13至16 mg（.）kg（-1.）d（-1），但半胱氨酸相对于蛋氨酸能满足多少仍有争议。本文综述了目前的状况，在体内估计蛋氨酸和半胱氨酸的需求，在人类成年人，并认为需要超出什么是必要的蛋白质合成。影响蛋氨酸和半胱氨酸利用率的因素，特别是那些导致一方面毒性或另一方面有益效果的条件，进行了讨论。关于甲基替代膳食来源的数据（例如，甜菜碱、胆碱、磷脂酰胆碱、S-腺苷甲硫氨酸、S-甲基甲硫氨酸）或硫（例如，N-乙酰半胱氨酸或L-2-氧代噻唑烷-4-羧酸）支持SAA“超越蛋白质”的作用。“其他途径可能会影响蛋氨酸和/或半胱氨酸的特定需求，特别是当人受到疾病，食物供应不足或环境压力的挑战时。
The intimate relation between amino acids and protein and nitrogen requirements is well recognized. Nutrition research has focused on the capacity of food to meet the need for nitrogen and indispensable amino acids (IAA) and led to the conclusion that the quality, not just the quantity, of protein is critical. This is especially relevant in regard to the sulfur amino acids (SAA) methionine and cysteine because of the increased understanding of their relation to chronic diseases (e.g., cardiovascular disease, dementia, cirrhosis), immunomodulation, DNA transcription, and RNA translation. Considerable effort has been expended to determine whether and to what extent cysteine can spare the requirement for the IAA methionine. In vivo studies in humans generally concur that the dietary requirement of the SAA ranges between 13 and 16 mg(.)kg(-1.)d(-1), but how much can be met by cysteine relative to methionine remains controversial. This review examines the current status of in vivo estimates of methionine and cysteine requirements in human adults and considers needs beyond what is necessary for protein synthesis. Factors influencing the utilization of methionine and cysteine, especially those conditions that lead to toxicity on the one hand or beneficial effects on the other, are discussed. Data on alternative dietary sources of methyl groups (e.g., betaine, choline, phosphatidylcholine, S-adenosylmethionine, S-methylmethionine) or sulfur (e.g., N-acetylcysteine or L-2-oxothiazolidine-4-carboxylic acid) support a role for the SAA "beyond protein." Other pathways may influence the specific requirement for methionine and/or cysteine, especially when the person is challenged by disease, inadequate availability of food, or environmental stress.