Gandía-Herrero Fernando, Jiménez-Atiénzar Mercedes, Cabanes Juana, Escribano Josefa, García-Carmona Francisco
Departamento de Bioquimica y Biologia Molecular A, Unidad Docente de Biologia, Facultad de Veterinaria, Universidad de Murcia, Espinardo, Murcia, Spain.
J Agric Food Chem. 2009 Mar 25;57(6):2523-8. doi: 10.1021/jf803608x.
Tyrosinase or polyphenol oxidase (EC 1.14.18.1) is one of the key enzymes for the biosynthesis of natural pigment betalains. These are an important class of water-soluble pigments, characteristic of plants belonging to the order Caryophyllales. In this work, dopamine-betaxanthin (also known as miraxanthin V) is reported as the pigment responsible for the bright coloration in yellow flowers of Portulaca oleracea (common purslane). The natural pigment is purified, and used as a substrate for the catecholase (diphenolase) activity of the enzyme tyrosinase. A new, continuous method to follow the activity is developed based on the fluorescent properties of the betaxanthin. Fluorescence of the enzyme activity derived products is reported for the first time. Relevance of the fluorescent phenomenon is discussed based on fluorescence images and the description of a physiological inner filter effect present in flowers of P. oleracea. The first description of the betalain content in flower pistils is also provided.
酪氨酸酶或多酚氧化酶（EC 1.14.18.1）是天然色素甜菜色素生物合成的关键酶之一。甜菜色素是一类重要的水溶性色素，是石竹目植物的特征性色素。在这项研究中，多巴胺 - 甜菜黄质（也称为米拉克黄质V）被报道为马齿苋黄色花朵中明亮颜色的色素来源。这种天然色素被纯化，并用作酪氨酸酶的儿茶酚酶（双酚酶）活性的底物。基于甜菜黄质的荧光特性，开发了一种新的、连续监测该酶活性的方法。首次报道了酶活性衍生产物的荧光。基于荧光图像以及对马齿苋花朵中存在的生理内滤效应的描述，讨论了荧光现象的相关性。同时还首次描述了花朵雌蕊中的甜菜色素含量。
