Wakamatsu Kazumasa, Ito Shosuke, Rees Jonathan L
Fujita Health University School of Health Sciences, Toyoake, Aichi, Japan.
Pigment Cell Res. 2002 Jun;15(3):225-32. doi: 10.1034/j.1600-0749.2002.02009.x.
Reductive hydrolysis of pheomelanin with hydriodic acid (HI) gives two aminohydroxyphenylalanine isomers, 4-amino-3-hydroxyphenylalanine ('specific AHP') and 3-amino-4-hydroxyphenylalanine (3-aminotyrosine, AT), which derive from the oxidative polymerization of 5-S-cysteinyldopa, and 2-S-cysteinyldopa, respectively. Since we first introduced this analytical method, the combined amount of AHP and AT ('total AHP') has been extensively used as a marker of pheomelanin. However, one problem with using total AHP as a marker is that background levels originate from precursors other than pheomelanin. Considerable and variable amounts of background AT are produced from other sources, most likely nitrotyrosine residues in proteins. In order to overcome this problem, we developed HPLC conditions which enable the direct injection of the HI reduction products into the HPLC system allowing good separation of AHP and AT. In this way we could study the importance of both degradation products separately and their specificity as markers for pheomelanin. The usefulness of the present method is validated using human hair samples of various colours which were divided into dark, fair or red colours. The combined amount of specific AHP and AT shows an excellent correlation with total AHP, and the amount of specific AHP also correlates with the amount of total AHP. We also examined total AHP and specific AHP values against pyrrole-2,3,5-tricarboxylic acid (PTCA) values in the human hair samples. These results show that specific AHP measurement gives a more prominent segregation for the ratio of specific AHP to PTCA among hairs of various colours than the ratio of total AHP to PTCA. Thus, we conclude that 'specific AHP' is a more specific marker of pheomelanin than is 'total AHP'.
用氢碘酸（HI）对褐黑素进行还原水解可得到两种氨基羟基苯丙氨酸异构体，即4-氨基-3-羟基苯丙氨酸（“特定AHP”）和3-氨基-4-羟基苯丙氨酸（3-氨基酪氨酸，AT），它们分别源自5-S-半胱氨酰多巴和2-S-半胱氨酰多巴的氧化聚合反应。自从我们首次引入这种分析方法以来，AHP和AT的总量（“总AHP”）已被广泛用作褐黑素的标志物。然而，将总AHP用作标志物存在一个问题，即背景水平源自褐黑素以外的前体物质。其他来源会产生大量且可变的背景AT，最有可能是蛋白质中的硝基酪氨酸残基。为了克服这个问题，我们开发了高效液相色谱（HPLC）条件，能够将HI还原产物直接注入HPLC系统，实现AHP和AT的良好分离。通过这种方式，我们可以分别研究这两种降解产物的重要性及其作为褐黑素标志物的特异性。使用各种颜色的人发样本（分为深色、浅色或红色）验证了本方法的实用性。特定AHP和AT的总量与总AHP显示出极好的相关性，特定AHP的量也与总AHP的量相关。我们还在人发样本中对照吡咯-2,3,5-三羧酸（PTCA）值检测了总AHP和特定AHP值。这些结果表明，在各种颜色头发中，特定AHP与PTCA的比值比总AHP与PTCA的比值具有更显著的区分度。因此，我们得出结论，“特定AHP”是比“总AHP”更特异的褐黑素标志物。
