Hu Jianan, Kulkarni Arun P
Department of Occupational Medicine, School of Public Health, Central South University, Changsha 410078, China.
Zhonghua Lao Dong Wei Sheng Zhi Ye Bing Za Zhi. 2002 Dec;20(6):409-12.
In order to explore the pathway of dealkylation of pesticides other than cytochrome P450 monocoxygenases, lipoxygenase (LOX)-mediated demethylation of aminocarb and some other pesticides were measured.
Formaldehyde generated in the reaction was estimated by Nash reaction to express the rate of demethylation of pesticides mediated by soy lipoxygenase (SLO).
N-demethylation of aminocarb mediated by SLO was found to depend on the incubation time, concentration of the enzyme, concentration of aminocarb and hydrogen peroxide. Under optimal conditions, Vmax value of 18 nmol of formaldehyde.min-1.nmol-1 of lipoxygenase was observed. The reaction exhibited Km values of 3.4 mmol/L for aminocarb and 235 mumol/L for hydrogen peroxide. A strong inhibition of the reaction by nordihydroguaiaretic acid, gossypol, and phenidone clearly implicated the lipoxygenase involvement as the protein catalyst. A significant decline in the formaldehyde accumulation in the presence of either reduced glutathione or dithiothreitol suggested generation of a free radical species as an initial oxidation intermediate during the demethylation of aminocarb by SLO. The inhibition of formaldehyde generation by butylated hydroxyanisole(BHT) and butylated hydroxy toluene(BHA) further supported this contention. In addition to aminocarb, seven other pesticides were also found to undergo N-demethylation, albeit at relatively low rates.
Certain pesticides may oxidatively undergo dealkylation via the lipoxygenase pathway in animals and plants.
为了探索除细胞色素P450单加氧酶之外的农药脱烷基化途径，对脂氧合酶（LOX）介导的灭害威及其他一些农药的去甲基化反应进行了测定。
通过纳什反应估算反应中生成的甲醛，以表示大豆脂氧合酶（SLO）介导的农药去甲基化速率。
发现SLO介导的灭害威N-去甲基化反应取决于孵育时间、酶浓度、灭害威浓度和过氧化氢浓度。在最佳条件下，观察到脂氧合酶的Vmax值为18 nmol甲醛·min⁻¹·nmol⁻¹。该反应对灭害威的Km值为3.4 mmol/L，对过氧化氢的Km值为235 μmol/L。去甲二氢愈创木酸、棉酚和非那吡啶对该反应有强烈抑制作用，这清楚地表明脂氧合酶作为蛋白质催化剂参与了反应。在存在还原型谷胱甘肽或二硫苏糖醇的情况下，甲醛积累显著下降，这表明在SLO介导的灭害威去甲基化过程中，有自由基物种作为初始氧化中间体生成。丁基羟基茴香醚（BHT）和丁基羟基甲苯（BHA）对甲醛生成的抑制作用进一步支持了这一观点。除灭害威外，还发现其他七种农药也会发生N-去甲基化反应，尽管速率相对较低。
某些农药在动植物体内可能通过脂氧合酶途径发生氧化脱烷基化反应。
