Properties Of Phenoloxidase(PO) From Lymantria Dispar (Linnaeus)and The Inhibitory Dynamics On Phenoloxidase Acitivity By Some Inhibitors

Phenoloxidase (PO), which is widely distributed in animals, plants and microorganism, is one of very important enzymes in insects. The enzyme have an important function in the development metamorphisis and immunity system of insects. In this paper we did some researches including comparison of properties of PO from Lymantria dispar (Linnaeus) in different stages and instars, the purification of the PO from Lymantria dispar (Linnaeus), properties of the enzyme and the effects of some factors on the activity of PO. The results were summarized as follows:1. The PO was purified by (NH4)2SO4 . Much of the activity existed in the deposition of 35% saturated (NH4)2SO4, and the yield was 67.94%, the fold of purification was 3.62. Then the enzyme was chromatographed on Sephadex G-100 gel filtration, the yield was 40.50%, the fold of purification was 7.04.2. The properties of PO showed that the optimum pH was 7.0 and the enzyme had a stable activity if the pH reaction system was between 6.5~7.5. The optimum temperature was 35℃, and the enzyme had a stable activity if the temperature reaction system was below 20℃. The kinetic parameter for the oxidation of catechol by PO was determined, the Km was 10.74 mmol·L-1. The Km was 3.19 mmol·L-1 for the oxidation of L-DOPA by PO.3. The effect of some metal ions on the PO activity was studied. The results showed that K+ had little influence on the enzyme activity, Ag+, Fe2+ and Fe3+inhibited the activity of the PO, Mg2+,Mn2+,Pb2+ and Zn2+ inhibited the enzyme activity when it was at the low concentration, and the activity was activitied by them when it was at a little high concentration. But Cu2+ and Cu+ activitied the enzyme activity when it was at the low concentration, and the activity was inhibited by Cu2+ and Cu+ when it was at a little high concentration..