Departamento de Bioquímica y Biología Molecular A, Unidad Docente de Biología, Facultad de Veterinaria, Universidad de Murcia, 30100, Espinardo, Murcia, Spain.
Planta. 2012 Jul;236(1):91-100. doi: 10.1007/s00425-012-1593-2. Epub 2012 Jan 24.
Betalains are water-soluble pigments with high antiradical capacity which bestow bright colors to flowers, fruits and other parts of most plants of the order Caryophyllales. The formation of the structural unit of all betalains, betalamic acid from the precursor amino acid 4,5-dihydroxyphenylalanine is catalyzed by the enzyme 4,5-DOPA-extradiol-dioxygenase followed by intramolecular cyclization of the 4,5-secodopa intermediate. This paper describes the purification and the molecular and functional characterization of an active 4,5-DOPA-extradiol-dioxygenase from the best-known source of betalains-Beta vulgaris-after heterologous expression in Escherichia coli. The enzyme is a monomeric protein with a molecular mass of 32 kDa characterized by chromatography, electrophoresis and MALDI-TOF analysis. Enzyme kinetic properties are characterized in the production of betalamic acid, the structural, chromophoric and bioactive unit of plant pigment betalains.
甜菜红素是一种水溶性色素，具有很强的抗自由基能力，为石竹目大多数植物的花、果实和其他部分赋予鲜艳的颜色。所有甜菜红素结构单元的形成是由酶 4,5-DOPA-外二醇-双加氧酶催化的，前体氨基酸 4,5-二羟基苯丙氨酸，然后是 4,5-色氨酸中间产物的分子内环化。本文描述了在大肠杆菌中异源表达后，从最著名的甜菜红素来源——甜菜（Beta vulgaris）中纯化和鉴定一种活性 4,5-DOPA-外二醇-双加氧酶，并对其进行了分子和功能特征分析。该酶是一种单体蛋白，分子量为 32 kDa，通过色谱、电泳和 MALDI-TOF 分析进行鉴定。酶动力学特性在甜菜红素的结构单元、生色单元和生物活性单元——甜菜酰胺酸的生成中进行了表征。
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