Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers-New Jersey Medical School, International Center for Public Health, 225 Warren Street, Newark, NJ, 07103, USA.
Department of Environmental Chemistry, University of Łódź, 90-236, Łódź, Poland.
Amino Acids. 2018 May;50(5):537-546. doi: 10.1007/s00726-018-2545-3. Epub 2018 Feb 26.
Growing human head hair contains a history of keratin and provides a unique model for studies of protein damage. Here, we examined mechanism of homocysteine (Hcy) accumulation and keratin damage in human hair. We found that the content of Hcy-keratin increased along the hair fiber, with levels 5-10-fold higher levels in older sections at the hair's tip than in younger sections at hair's base. The accumulation of Hcy led to a complete loss of keratin solubility in sodium dodecyl sulfate. The increase in Hcy-keratin was accompanied by a decrease in methionine-keratin. Levels of Hcy-keratin were correlated with hair copper and iron in older hair. These relationships were recapitulated in model experiments in vitro, in which Hcy generation from Met exhibited a similar dependence on copper or iron. Taken together, these findings suggest that Hcy-keratin accumulation is due to copper/iron-catalyzed demethylation of methionine residues and contributes to keratin damage in human hair.
人类头发生长过程中会积累角蛋白，并为蛋白质损伤研究提供独特的模型。在这里，我们研究了同型半胱氨酸（Hcy）在人发中积累和角蛋白损伤的机制。我们发现 Hcy-角蛋白的含量沿发纤维增加，发梢较老部位的水平比发根较新部位高 5-10 倍。Hcy 的积累导致角蛋白在十二烷基硫酸钠中的溶解度完全丧失。Hcy-角蛋白的增加伴随着蛋氨酸-角蛋白的减少。在较老的头发中，Hcy-角蛋白的水平与头发中的铜和铁有关。这些关系在体外模型实验中得到了重现，其中 Met 产生的 Hcy 对铜或铁的依赖性相似。总之，这些发现表明 Hcy-角蛋白的积累是由于铜/铁催化的蛋氨酸残基去甲基化所致，并导致了人类头发中角蛋白的损伤。
