INVOLVEMENT OF PEROXIDASE IN CHORION HARDENING IN AEDES-AEGYPTI

Peroxidase activity is detectable in Aedes aegypti ovaries, containing developing eggs, at 24 h following blood feeding, and peak peroxidase activity is reached at 36-48 h after the blood-meal. Peroxidase is as sociated with the chorion layer in mature eggs and the majority of the enzyme is released from the chorion layer by treating the isolated ch orion fraction with SDS/urea. Analysis of the SDS/urea solubilized cho rion proteins using SDS-PAGE with tropolone/H2O2 or dopa staining veri fied the presence of both peroxidase and phenol oxidase in the release d chorion proteins, The molecular weight of chorion peroxidase is abou t 61,000 Da as determined by SDS-PAGE analysis, Incubation of the solu bilized chorion proteins with tyrosine and H2O2 produces dityrosine, a nd hyrolysis of hardened egg chorion results in the detection of dityr osine and trityrosine in the chorion hydrolysate, Data suggest that ch orion peroxidase is involved in the hardening of the mosquito egg chor ion by catalyzing the formation of ditryrosine through tyrosine residu es on structural proteins, The overall hardening of the A. aegypti egg chorion includes both peroxidase-mediated chorion protein crosslinkin g through dityrosine formation and phenol oxidase-catalyzed chorion me lanization.