Escribano Josefa, Gandía-Herrero Fernando, Caballero Nuria, Pedreño Maria Angeles
Departamento de Bioquímica y Biología Molecular A, Unidad Docente de Biología, Facultad de Veterinaria, Universidad de Murcia, E-30100 Espinardo, Murcia, Spain.
J Agric Food Chem. 2002 Oct 9;50(21):6123-9. doi: 10.1021/jf020356p.
The two enzymes involved in enzymatic browning reactions, polyphenol oxidase (PPO) and peroxidase (PO), have been partially purified and extracted from different fractions of beet root. PPO is mainly located in the membrane fraction, and it was also found in the soluble fraction. In both cases PPO was in its latent state. However, PO activity was higher in the soluble fraction than in the membrane fraction. Nevertheless, the highest values of specific activity for PO were obtained from the solubilized enzyme from acetone powders. Under native isoelectric focusing (IEF), several PPO isoenzymes were present in the pH range of 4.8-5.8. All of these isoenzymes shared a single band with a similar apparent mass under sodium dodecyl sulfate-polyacrylamide gel electrophoresis. PO was also analyzed by IEF, showing a complex isoenzyme pattern in all fractions. The characteristic basic PO isoenzyme of high pI found in both the soluble fraction and the solubilized enzyme from acetone powders was not detected in the membrane fraction. The kinetic characterization of PPO and PO from all fractions was carried out.
参与酶促褐变反应的两种酶，即多酚氧化酶（PPO）和过氧化物酶（PO），已从甜菜根的不同组分中部分纯化并提取出来。PPO主要位于膜组分中，在可溶组分中也有发现。在这两种情况下，PPO均处于潜伏状态。然而，PO活性在可溶组分中比在膜组分中更高。尽管如此，PO的比活性最高值是从丙酮粉溶解的酶中获得的。在天然等电聚焦（IEF）条件下，在4.8 - 5.8的pH范围内存在几种PPO同工酶。在十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳下，所有这些同工酶都共享一条具有相似表观质量的条带。PO也通过IEF进行分析，在所有组分中显示出复杂的同工酶模式。在膜组分中未检测到在可溶组分和丙酮粉溶解的酶中均发现的高pI特征性碱性PO同工酶。对所有组分中的PPO和PO进行了动力学表征。
