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Indian Journal of Biochemistry and Biophysics (IJBB) >
IJBB Vol.45 [2008] >
IJBB Vol.45(3) [June 2008] >
| Title: | Inhibitory effects of 2-hydroxybenzaldehyde on the activity of phenoloxidase from Pieris rapae (Lepidoptera) larvae |
| Authors: | Xue, Chao-Bin
Luo, Wan-Chun
Chen, Qing-Xi
Ma, De-Ying
Wang, Qin |
| Keywords: | Phenoloxidase
Inhibition kinetics
2-Hydroxybenzaldehyde
Monophenolase
Diphenolase
Pieris rapae (L.) |
| Issue Date: | Jun-2008 |
| Publisher: | CSIR |
| Abstract: | Phenoloxidase (PO) is a key enzyme in insect development, responsible for catalyzing the hydroxylation of tyrosine
into O-diphenols and oxidation of O-diphenols into O-quinones. In the present study, the kinetic assay for PO from Pieris
rapae (L.) larvae was performed in air-saturated solutions and its kinetic behavior in the oxidation of L-tyrosine (a
monophenol) and L-DOPA (L-3, 4-dihydroxyphenylalanine, a diphenol) was studied. The inhibitory effects of
2-hydroxybenzaldehyde (2-HBD) on the monophenolase and diphenolase activities of PO were also studied. Results showed
that 2-HBD inhibit both the monophenolase and diphenolase activities of PO. The lag period of L-tyrosine oxidation
catalyzed by the enzyme was lengthened and the steady-state activity of the enzyme sharply decreased. The inhibitor was
found to be noncompetitively reversible with a KI (KI = KIS) of 1.21 mmol/L and an estimated IC₅₀ of 8.08 ± 0.11 mmol/L
for monophenolase and 4.14 ± 0.08 mmol/L for diphenolase activities. In the time-course of oxidation of L-DOPA catalyzed
by the enzyme in the presence of different concentrations of 2-HBD, the rate decreased with increasing time until a straight
line was reached. The microscopic rate constants for the reaction of 2-HBD with the enzyme were determined. |
| Page(s): | 184-191 |
| ISSN: | 0301-1208 |
| Source: | IJBB Vol.45(3) [June 2008]
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