The sulfur-containing amino acids: An overview
The sulfur-containing amino acids: An overview
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DOI：
10.1093/jn/136.6.1636s
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发表时间：
2006-06-01
影响因子：
4.2
通讯作者：
Brosnan, Margaret E.
中科院分区：
文献类型：
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作者：
Brosnan, John T.;Brosnan, Margaret E.
蛋氨酸、半胱氨酸、同型半胱氨酸和牛磺酸是4种常见的含硫氨基酸，但只有前2种被掺入蛋白质中。在元素周期表中，硫与氧属于同一族，但其电负性要小得多。这种差异解释了含硫氨基酸的一些独特性质。甲硫氨酸是几乎所有真核生物蛋白质合成的起始氨基酸; N-甲酰甲硫氨酸在原核生物中具有相同的功能。在蛋白质中，许多甲硫氨酸残基埋在疏水性核心中，但一些暴露的甲硫氨酸残基容易受到氧化损伤。半胱氨酸，凭借其形成二硫键的能力，在蛋白质结构和蛋白质折叠途径中起着至关重要的作用。甲硫氨酸代谢始于其活化为S-腺苷甲硫氨酸。这是一种非常通用的辅因子，在甲基转移、5 '-脱氧腺苷基转移、多胺合成、植物乙烯合成等许多方面发挥作用。在动物中，大部分S-腺苷甲硫氨酸用于甲基化反应。S-腺苷高半胱氨酸是这些甲基转移酶的产物，产生高半胱氨酸。同型半胱氨酸可以通过转硫途径再甲基化为甲硫氨酸或转化为半胱氨酸。蛋氨酸也可以通过转氨途径代谢。该途径仅在高蛋氨酸浓度下才有意义，产生许多有毒终产物。半胱氨酸可转化为谷胱甘肽和牛磺酸等重要产物。牛磺酸在许多组织中的浓度高于任何其他氨基酸。它是猫的必需营养素。
Methionine, cysteine, homocysteine, and taurine are the 4 common sulfur-containing amino acids, but only the first 2 are incorporated into proteins. Sulfur belongs to the same group in the periodic table as oxygen but is much less electronegative. This difference accounts for some of the distinctive properties of the sulfur-containing amino acids. Methionine is the initiating amino acid in the synthesis of virtually all eukaryotic proteins; N-formylmethionine serves the same function in prokaryotes. Within proteins, many of the methionine residues are buried in the hydrophobic core, but some, which are exposed, are susceptible to oxidative damage. Cysteine, by virtue of its ability to form disulfide bonds, plays a crucial role in protein structure and in protein-folding pathways. Methionine metabolism begins with its activation to S-adenosylmethionine. This is a cofactor of extraordinary versatility, playing roles in methyl group transfer, 5'-deoxyadenosyl group transfer, polyamine synthesis, ethylene synthesis in plants, and many others. In animals, the great bulk of S-adenosylmethionine is used in methylation reactions. S-Adenosylhomocysteine, which is a product of these methyltransferases, gives rise to homocysteine. Homocysteine may be remethylated to methionine or converted to cysteine by the transsulfuration pathway. Methionine may also be metabolized by a transamination pathway. This pathway, which is significant only at high methionine concentrations, produces a number of toxic endproducts. Cysteine may be converted to such important products as glutathione and taurine. Taurine is present in many tissues at higher concentrations than any of the other amino acids. It is an essential nutrient for cats.