Abstract:

The inhibitory effects of tetra-hexylresorcinol and kojic acids on the phenoloxidase from Lymantria dispar were investigated. The results showed that the IC₅₀ of tetra-hexylresorcinol was 0.000　41 mmol·L^-1 for monophenolase activity and 0.000　35 mmol·L^-1 for diphenolase， respectively. Tetra-hexylresorcinol extended the lagtime of the enzyme for oxidation of L-tyrosine. The lagtime extended from 181 s to 253　s by 4-hexylresorcinol with 0.000　2 mmol·L^-1, and the lagtime extended from 181 s to 372　s by the chemical with 0.000　5 mmol·L^-1. The inhibition kinetics analyzed by Lineweaver-Burk plots indicated that 4-hexylresorcinol was a competitive inhibitor for the oxidation of catechol and the inhibition constant was 0.000　15 mmol·L^-1.The IC₅₀ of kojic acids were 0.06 mmol·L^-1 for monophenolase activity and 0.92 mmol·L^-1 for diphenolase, respectively. Kojic acids extended the lagtime of the enzyme for oxidation of L-tyrosine. The lagtime extended from 306 s to 702　s by the kojic acids with 0.1 mmol·L^-1, and the lagtime extended from 306 s to 900　s by the compound with 0.15 mmol·L^-1. The inhibition kinetics analyzed by Lineweaver-Burk plots indicated that kojic acids was a competitive inhibitor for the oxidation of catechol, and the inhibition constant was 0.51 mmol·L^-1.

Key words: Lymantria dispar, phenoloxidase, inhibitory mechanism, tetra-hexylresorcinol, kojic acids