Yoshimura T, Kamataki T, Miura T
Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Anal Biochem. 1990 Jul;188(1):132-5. doi: 10.1016/0003-2697(90)90540-p.
Histamine reacts with ortho-phthalaldehyde (OPA) in an alkaline medium to form an unstable fluorescent adduct (Fbase-Hm). Acidification of the solution to pH 2-4 gives a stable and highly fluorescent adduct (Facid-Hm). In contrast, histidine develops a relatively stable fluorescent adduct (Fbase-Hd) with OPA in an alkaline medium. Upon acidification of the solution, however, only trace amounts of the alternative fluorescent adduct (Facid-Hd) are produced although Fbase-Hd disappears similarly to Fbase-Hm. In this paper, the reaction pathway of histidine with OPA was clarified by the kinetic analysis of formation and degradation of Fbase-Hd. In comparing the results of this study with the previous ones for histamine (T. Yoshimura et al., 1987, Anal. Biochem., 164, 132-137), we elucidate the difference between histamine and histidine in the mechanism of fluorescence reaction with OPA. The presence of the carboxyl group in histidine not only stabilizes Fbase-Hd in an alkaline medium but also prevents the formation of a 1:2 adduct of histidine and OPA, the precursor of Facid-Hd.
组胺在碱性介质中与邻苯二甲醛（OPA）反应形成不稳定的荧光加合物（Fbase-Hm）。将溶液酸化至pH 2-4会得到稳定且高度荧光的加合物（Facid-Hm）。相比之下，组氨酸在碱性介质中与OPA形成相对稳定的荧光加合物（Fbase-Hd）。然而，溶液酸化后，尽管Fbase-Hd与Fbase-Hm一样消失，但仅产生痕量的替代荧光加合物（Facid-Hd）。在本文中，通过对Fbase-Hd形成和降解的动力学分析，阐明了组氨酸与OPA的反应途径。将本研究结果与之前关于组胺的研究结果（T. Yoshimura等人，1987年，《分析生物化学》，164，132-137）进行比较，我们阐明了组胺和组氨酸在与OPA荧光反应机制上的差异。组氨酸中羧基的存在不仅在碱性介质中稳定了Fbase-Hd，还阻止了组氨酸与OPA的1:2加合物（Facid-Hd的前体）的形成。
