Dissertation > Excellent graduate degree dissertation topics show

Inhibitory Effects of Schiff Analogs on Insect Phenoloxidase

Author: XiaoZuo
Tutor: LuoWanChun
School: Shandong Agricultural University
Course: Pesticides
Keywords: phenoloxidase (PO) schiff kinetics inhibitory mechanism
CLC: S481
Type: Master's thesis
Year: 2008
Downloads: 81
Quote: 1
Read: Download Dissertation

Abstract

Phenoloxidase （PO）（EC.1.14.18.1） also known as tyrosinase, is a structure-complex and multifunctional copper-containing enzyme, which widely distributed among animals, plants, fungi, and prokaryotes. PO is thought to be involved in many biological processes of invertebrates, such as consenescence of human body, wound healing, fruits and vegetables browning and pigment formation. It is one of the key enzymes in the development process of insects, the enzyme possesses an important function in metamorphism developing and immunity system. Currently, many studies focused on this field.Based on the present paper, compounds Schiff analogs of salicylidene aniline ect. were designed and synthesized in my laboratory, and were selected as the PO inhibitors to determine the inhibitory effects against the enzyme. Besides, the kinetics inhibition of PO were studied using the higher activity compounds in this thesis. Based on the results published previously in my laboratory, Bio-assay of several componds which could inhibit PO activity better was carried out for controlling 2nd Plutella xylostella. The contents and results were summarized as follows:1 The effects of nine Schiff analogs of salicylidene aniline on partially purified PO from Pieris rapae L. were investigated. The results indicated that 5 compounds （Salicylidene-aniline, Salicylidene-3-chloroaniline, Salicylidene -4 -chloroaniline, Salicylidene-4-bromoaniline, salicylidene-4-nitroaniline） could inhibit PO activity observably, and the inhibitor concentrations leading to a loss of 50% activity （IC50） were estimated to be 0.025 mmol·L^-1, 0.351 mmol·L^-1, 0.732 mmol·L^-1, 0.471 mmol·L^-1, and 0.675 mmol·L^-1, respectively. Meanwhile, all the inhibitors showed reversible competitive inhibition, except salicylidene-4-nitroaniline, which showed reversible mixed inhibition. The KI values were determined as 0.106 mmol·L^-1, 0.735 mmol·L^-1, 10.059 mmol·L^-1, 8.390 mmol·L^-1, and 20.198 mmol·L^-1 for the 5 compounds, respectively. The UV-visible spectra of Salicylidene-aniline and salicylidene -4-nitroaniline in the presence of copper ions and the enzyme showed that Salicylidene-aniline could directly chelate the copper ions of PO; however, salicylidene-4-nitroaniline could neither chelate the additional copper ions nor the copper ions of PO.2 The inhibitory effects of nine schiff analogs of 2-hydroxy-4- methoxybenzylidene-aniline as inhibitors on PO from P. rapae, which had been partially purified, was studied by using microtitration assay. The results showed that 2-hydroxy-4-methoxybenzylidene-aniline and 2-hydroxy-4- methoxybenzylidene-3-chloroaniline could inhibit PO activity evidently and the inhibitor concentration leading to 50% activity loss （IC50） was estimated to be 0.116 mmol/L, 0.051 mmol/L, respectively. 2-hydroxy-4-methoxy- benzylidene-aniline was found to be a reversible noncompetitive inhibitor, and the KI value was determined to be 1.96 mmol/L for the compound. Although the compound could affect PO directly, it did not chelate copper of PO active center.3 The inhibitory effects of nine schiff analogs of 2-hydroxy-3- methoxybenzylidene-aniline as inhibitors on PO from P. rapae, were studied by using microtitration assay. The results showed that the tested compounds 2-hydroxy-3-methoxybenzylidene-aniline , 2-hydroxy-3-methoxybenzylidene -4-nitroaniline , 2-hydroxy-3-methoxybenzylidene-3-chloroaniline , 2-hydroxy -3-methoxybenzylidene-3,4-dichloroaniline could inhibit PO activity remarkably and the IC50 was estimated to be 0.013 mmol·L-1, 0.385 mmol·L-1, 0.334 mmol·L-1and 0.059 mmol·L-1, respectively. The inhibitors were all found to be reversible competitive inhibitors.4 Bio-assay of several componds which could inhibit PO activity for controlling Plutella xylostella larva were carried out and the results showed that the“lethal”effects or so called as“killer”on Plutella xylostella larva was not obvious, instead, the PO inhibitors should be named“potential insect regulators with novel mode of action”.

Related Dissertations

CLC: > Agricultural Sciences > Plant Protection > Pesticide ( chemical control ) > Plant chemical protection theory
© 2012 www.DissertationTopic.Net Mobile