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Enzymatic properties of phenoloxidase from Pieris rapae (Lepidoptera) larvae
Author(s) -
XUE CHAOBIN,
LUO WANCHUN,
CHEN QINGXI,
WANG QIN,
KE LINA
Publication year - 2006
Publication title -
insect science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.991
H-Index - 45
eISSN - 1744-7917
pISSN - 1672-9609
DOI - 10.1111/j.1744-7917.2006.00091.x
Subject(s) - pieris rapae , lepidoptera genitalia , biology , instar , substrate (aquarium) , enzyme , michaelis–menten kinetics , larva , enzyme assay , nuclear chemistry , botany , biochemistry , chemistry , ecology
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 ( K m ) and maximal velocity ( V m ) 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 IC 50 of 1.50 and 1.12 μmol/L, respectively. The inhibition constants were estimated to be 0.50 and 0.47 μmol/L, respectively.