Inhibitory effects of 4-dodecylresorcinol on the phenoloxidase of the diamondback moth Plutella xylostella (L.) (Lepidoptera Plutellidae)

Abstract Phenoloxidase (PO) is a key enzyme in the developmental process of insects that is responsible for catalyzing the hydroxylation of monophenols and the oxidation of o -diphenols. In the present investigation, the PO of Plutella Xylostella (L.)(Lepidoptera Plutellidae) was partially purified with 40% saturated (NH 4 ) 2 SO 4 and Sephadex G-100 gel filtration, and the effects of 4-dodecylresorcinol on the monophenolase and o -diphenolase activity of PO were studied. The results showed that 4-dodecylresorcinol could inhibit monophenolase and o -diphenolase activity. In addition, following 4-dodecylresorcinol treatments, the lag time of PO for oxidation of l -tyrosine was obviously lengthened and the steady-state activity was decreased. The inhibitor was found to be competitively reversible with a K i of 0.201 mM and an estimated IC 50 (inhibition concentration showing 50% of the maximum inhibition) of 0.160 mM for monophenolase and 0.369 mM for diphenolase. The ability of 4-dodecylresorcinol to inhibit PO activity may be associated with its ability to directly affect copper at the active site