Enzymatic properties of phenoloxidase from Pieris rapae (Lepidoptera) larvae.

Chao-Bin Xue; Wan-Chun Luo; Qing-Xi Chen; Qin Wang; Li-Na Ke

The kinetic parameters of partially purified phenoloxidase (PO, EC. 1.14.18.1) from the 5th instar larvae of Pieris rapae (Lepidoptera) were determined, using L-3, 4-dihydroxyphenylalanine (L-DOPA) as substrate. The optimal pH and temperature of the enzyme for the oxidation of L-DOPA were determined to be at pH 7.0 and at 42°C, respectively. The enzyme was stable between pH 6.5 and 7.4 and at temperatures lower than 37°C. At pH 6.8 and 37°C, the Michaelis constant ( Km) and maximal velocity ( Vm) of the enzyme for the oxidation of L-DOPA were determined to be 0.80 μmol/L and 1.84 μmol/ L/min, respectively. Tetra-hexylresorcinol and 4-dodecylresorcinol effectively inhibited activity of phenoloxidase and this inhibition was reversible and competitive, with the IC50 of 1.50 and 1.12 μmol/L, respectively. The inhibition constants were estimated to be 0.50 and 0.47 μmol/L, respectively.

PIERIS rapae; DOPA; OXIDATION; HYDROGEN-ion concentration; ENZYMATIC analysis

Insect Science, 2006, Vol 13, Issue 4, p251

1672-9609

Academic Journal

10.1111/j.1744-7917.2006.00091.x