Purification And Thermostability Of Peroxidase From Ginkgo Biloba L.leaves

Peroxidase (POD, EC 1.11.1.7) is an oxidase that contains a hemachrome group and which exits extensively in every living creature like animal, plant, and microorganism. It also contains metal ions such as iron or copper and has not identical structure and catalytic mechanism. It serves a number of different functions, such as protecting cell from the damage of poisonous peroxide; eliminating hydrogen peroxide; playing an important role in the biological degradation of lignin; been concerning with cell wall and growth hormone synthesis, recovering tissue damage; cooperating with SOD each other eliminating superfluous free radical and maintaining it in a normal dynamic level in vivo so as to enhance vegetable resistant capability in bad environment, etc.Ginkgo biloba is one kind of archaic plant, that contemporaneous with dinosaur, proper species of trees in China. Its fruits and leaves have important pharmaceutical value. There are lots of researches on chemical constituent and pharmaceutical function about G biloba in home and abroad. The results show that G biloba leaves and EGB (extracts from G biloba leaves) play an important function on curing cerebrovascular disease and hyperlipemia, and also have good curative effect on diseases with respiratory system and neurological disease. However, there is few information about POD in G. biloba leaves. Isolation, purification, and characterization of POD in G. biloba leaves were performed in this experiment, and the main results as follows:1. Holistic isoperoxidase (apparent enzyme activity), optimum pH, and influence of trehalose on activity.The isoperoxidase from G biloba leaves have high thermostablity. The results suggested that the activity remained 78% and 39% at the condition of 40℃and 50℃disposing 30 minutes, respectively, and at 60℃, 70℃, 80℃the POD activity could maintain for 27 minutes, 18 minutes and 3 minutes, respectively. The optimum pH of POD in G biloba leaves was 6.4 and 9.2, respectively. Trehalose could protect the POD thermostablity, especially at 50℃60℃70℃. And after dealing with trehalose, optimum pH of the POD acitivity changed from 6.4 and 9.2 to 6.6 and 9.4, respectively.2. Purification of POD from G. biloba leaves.In this research, we have separated one sort of isoperoxidase from G biloba leaves using ammonium sulfate, Sephadex G-100 and DEAE-A52 cellulose. 17.41-fold and a 15.3% yield were obtained. Both PAGE and SDS-PAGE showed one band.3. Characterization of the purified POD from G biloba leaves.Some Characterization of the purified POD from G. biloba leaves was investigated. The optimum pH and temperature was 5.8 and 37℃, respectively; it has high thermostablity, and the activity could remain 52% and 11% at the condition of 50℃and 60℃disposing 30 minutes, respectively; the POD activity can maintain for 24 minutes and 6 minutes at 70℃and 80℃, separately; trehalose could improve thermostablity of the POD, and change its optimum pH from 5.8 to 6.2.