Purification and biochemical characterization of phenoloxidase from hemolymph of Glyphodes pyloalis (Lep: Pyralidae)

Insect phenoloxidase (PO) (EC 1.14.18.1) is the key enzyme in development and immunity of insects. Inhibition of this enzyme could be a new target for pest control. The lesser mulberry snout moth, Glyphodes pyloalis Walker is an important pest of mulberry trees in north of Iran. This pest feeds on mulberry leaves and causes serious problems for the silk industries. In this study, PO from hemolymph of G. pyloalis was purified by ammonium sulfate precipitation, ion exchange chromatography and gel filtration. The apparent molecular weights of two isoforms were determined by SDS-PAGE as 69.66 and 70.53 KDa. The inhibitory kinetics of PO showed that the mechanisms were competitive and mixed inhibition for 4-hexylresorcinol, kojic acid and quercetin, respectively. Optimal pH and maximum temperature for PO activity purified from G. pyloalis were 7 and 35 °C, respectively. The purified PO was stable at 40, 45 and 50 ºC for 30 min. The effects of different ions on enzyme activity showed that Zn2 had a significant inhibitory effect.