Primary Studies On The Phenoloxidase From The Haemolymph Of Larvae Of Heliothis Armigera

Ovomermis sinensis Chen et al.,1991 is a kind of insect-parasitic nematode.Many insect species are susceptible to this nematode,and most of them are lepidopteron, for example,Heliothis armigera,Leucania separata,Prodenia litura,igrotis ypsilon,Spodoptera exigua,Plutella xylostella etc.The insect hosts invariably die when the juvenile nematodes complete their parasite development and exit from the host's hemocoel.The nematode can't infect man and domestic animals,and can't do damage to enviroment,so it has potential for the biological control of a wide range of insect pests.As a natural biological control agent, Ovomermis sinensis has a bright future in application and an important significance in science reseach.Heliothis armigera is a kind of very important pest in agriculture,and causes great economic loss in our country and other countries every year. As a kind of insect, Heliothis armigera has its special immunity system,which is made up of by cellular immunity and humoral immunity. Phenoloxidase plays an important role in insect's humoral immunity. Heliothis armigera's humoral immunity will be sure to be affected, including the activity of phenoloxidase after infection with Ovomermis sinensis. These changes will affect the development and growth of the nematodes. So it is in favor of the effect of this nematode as a kind of natural biological control agent if these changes are understood. This thesis has studied the activity changes in phenoloxidase in the haemolymph of larvae of Heliothis armigera. The results showed that on the first day in infection, Ovomermis sinensis caused increase in phenoloxidase activity in infected group which is 1.12 times compared with control group at the same time; but in the left time of infection, the activity of phenoloxidase were inhibited by the nematodes, and on the fifth day the inhibition reached the highest degree. On this day, the phenoloxidase activity of control group is 1.52 times compared with the infected group.It requires to purificate phenoloxidase in order to study the biochemicalcharacterization of this enzyme thorough and illustrate it's catalyze mechanism.The proteins of haemolymph was seperated by means of native electrophoresis in polyacrylamide gel and identified based on isozyme. The PAGE resulted in 3 MPO-positive bands and 2 DPO-positive bands. The isoelectric point of two kinds of DPO were both 5.49 by means of isolectric focusing gel electrophoresis(IEF); but the result of MPO was not good. The enzyme was purified by 40% saturated (NH4)2SO4 and Sephadex G-200 gel filtration from crude enzyme with purification factor of 41.5, and yield factor of 12.7%, and the specific activity 4030.6U/mg. The enzyme was purified partially.