Study On The Phenoloxidase Of The Diamondback Moth Plutella Xylostella (L.)(Lepidoptera Plutellidae) And Its Inhibitors

Phenoloxidase (PO, EC.1.14.18.1), is a copper-containing enzymewidely distributed in plants , microorganisms and animals. Thismultifunctional enzyme catalyzes two distinct reactions, the hydroxylation ofmonophenol to o-diphenol (monophenolase activity) and the conversion ofo-diphenol to the corresponding o-quinone (diphenolase activity). In insects,phenoloxidase is also a widely distributed enzyme playing important roles innormal developmental processes, such as cuticular tanning, scleration,wound healing, production of opsonins, and encapsulation and noduleformation for defense against foreign pathogens. In the present paper we havedone research on the purification of PO from the diamondback moth P.Xylostella (L.) (Lepidoptera Plutellidae), the properties of the enzyme and theeffects of some effectors on its activity. The results could be summarized asfollows:1. The PO was purified by (NH4)2SO4. Much of the activity was in thedeposition of 40% saturated (NH4)2SO4, PO was purified 4.525-fold with arecovery of 68.09%. After the enzyme was chromatographed on SephadexG-100 gel filtration, PO was purified 6.526-fold with a recovery of 31.21%.2. The activity of PO from P. Xylostella (L.) in different stages and instarswas different. The activity was gradualy improved with the instars increased,however, it was decreased in the pupal period. The enzyme activity of the 4thinstar larva was the highest.3. The properties of PO showed that the optimum pH was 6.5 and theenzyme would have a stable activity if the pH reaction system is between 6.5 ~7.0; The optimum temperature was 35℃, and the enzyme had a stableactivity if the temperature reaction system is between 25 ~ 40℃.4. The effect of some metal ions on the PO activity was studied. The...