甲基毒死蜱对红细胞乙酰胆碱酯酶的抑制作用及其与膜脂相互关系

以人红细胞膜为材料,研究了甲基毒死蜱与膜上乙酰胆碱酯酶的相互作用及其与膜脂的关系。结果显示,甲基毒死埤对人红细胞ＡＣｈＥ有明显的抑制作用,与膜温育３０ｍｉｎ,其半数抑制浓度约为０．１０ｍｍｏｌ／Ｌ。动力学分析表明,其抑制作用为非竞争性。０．２％Ｔｒｉｔｏｎ Ｘ－１００并不改变ＡＣｈＥ对甲基毒死蜱的敏感性,亦即ＡＣｈＥ上甲基毒死蜱的作用部位与其所处的脂质微环境无关。     

硫酸镍对人红细胞膜Na~+、K~+、Ca~(2+)-ATP酶及乙酰胆碱酯酶活力的影响

实验研究了硫酸镍对人红细胞膜Na+、K+、Ca2+-ATP酶及乙酰胆碱酯酶(AChE)活力的影响,为从分子水平阐明镍毒作用机理及为探索防治措施提供依据。结果表明,硫酸镍对此三种酶均有抑制作用,并呈现较高的量效关系及时效关系。     

山莨菪碱对人红细胞膜蛋白及膜脂运动的影响

本文采用自旋标记顺磁共振波谱技术,研究了山茛菪碱对人红细胞膜蛋白和膜脂运动的影响.结果表明:用马来酰亚胺标记的人红细胞膜,加入山茛菪碱后,其顺磁共振波谱中强、弱固定化作用谱的峰值比增大,膜蛋白的运动受到限制.山茛菪碱对红细胞膜脂的作用部位主要在极性头部,并影响膜脂的流动性.本文还对山茛菪碱与红细胞膜作用的可能机制进行了讨论.     

红细胞膜的影细胞蛋白

一、发现哺乳动物(包括人)的红细胞膜蛋白在重量上约占膜总重量的50%。人红细胞膜经十二烷基硫酸钠处理、聚丙烯酰胺凝胶电泳和考马斯亮蓝染色后,至少可见14条谱带,多则可染21条,其中有12条与膜支架(skeleton)有关。最主要的一种支架蛋白叫影细胞蛋白(spec-trin),它既是红细胞膜支架的基本成份,又是红细胞膜的一种收缩性蛋白。影细胞蛋白首先是Marchesi与Steers利用豚鼠红细胞膜的血影(ghost)为材料,在5%聚丙烯酰胺(含8M     

稀土离子对磷脂酰胆碱脂质体及人红细胞膜自由基氧化的影响

通过荧光和电泳方法研究了稀土离子对磷脂酰胆碱（PC）脂质体及人红细胞膜脂质过氧化的影响．结果表明稀土离子（除钇外）都能够强烈的抑制膜的脂质过氧化,其作用强度随不同的稀土离子可有较大的差别．稀土离子对分离的人红细胞膜的脂质过氧化的抑制作用比对PC脂质体更强．但是,对完整红细胞用稀土离子处理反而会导致膜的脂质过氧化大大加强．     

稀土离子对磷脂酰胆碱脂质体及人红细胞膜自由基氧化的影响

通过荧光和电泳方法研究了稀土离子对磷脂酰胆碱脂质体及人红细胞膜脂持过氧化的影响。结果表明稀土离子都能够强烈的抑制膜的脂质过氧化,春作用强度随不同的稀土离子要有较大的判别稀土离子对分离的人红细胞膜的脂质过氧化的抑制作用比对ＰＣ脂质体更强。     

酶标板法监测棉蚜乙酰胆碱酯酶对杀虫剂的不敏感性

用酶标板法测定了不同浓度有机磷和氨基甲酸酯杀虫剂在反应不同时间内对棉蚜Aphis gossypii乙酰胆碱酯酶(AChE)的抑制作用。结果表明有机磷杀虫剂甲基1605,辛硫磷,久效磷,氧乐果和乙酰甲胺磷对棉蚜AChE均无明显的抑制作用。当用0.01 mol/L灭多威与酶及底物反应1 h对北京棉蚜(敏感)种群AChE的抑制率可达82.4%,与反应2 h 89.4%仅差7%。因此以0.01 mol/L灭多威反应1 h测定棉蚜AChE对它的敏感性是合理的。通过测定北京地区寄主为鼠李和棉花以及山东高密寄主为棉花的棉蚜种群中个体AChE活性的分布和灭多威对其抑制的分布,表明3个棉蚜种群中AChE个体频率的分布差异不大,而灭多威对三个种群个体AChE的抑制率小于30%的个体分别为2.4%、16%和29%。抑制率大于70%的个体分别为72%、33%和1%,与生物测定结果一致。因此,用酶标板法测定棉蚜个体AChE对氨基甲酸酯的不敏感性频率可作为棉蚜对氨基甲酸酯抗性的监测技术,为棉蚜化学防治提供依据。     

胰蛋白酶对红细胞膜生物物理特性的影响

通过胰蛋白酶作用于红细胞膜,造成红细胞膜不同程度的损伤,改变其膜的生物物理特性。采用新型激光衍射法测量了上述血样的弹性模量Ｅ和膜粘度μｍ。同时通过ＤＰＨ标记的萤光偏振法测定了这些红细胞膜的流动性,并采用ＭＳＬ标记的电子自旋共振波谱技术（ＥＳＲ）测量了红细胞膜蛋白构象的动态变化,对上述红细胞膜结构改变所引起的微观流变特性的变化进行了初步探讨。     

几种有机磷杀虫剂使家蝇中毒后对真、假胆碱酯酶的抑制作用

本文用测压法研究了敌百虫、乐果、酰脲磷对家蝇体内外真胆碱脂酶(AChE)、假胆碱酯酶(φChE)的抑制效能与中毒征状的关系,并以N-甲基氨基甲酸苯酯进行了比较。所得结果表明,所用药剂对家蝇的中毒征状与对AChE和φChE的抑制情况紧密相关,而对AChE的抑制作用比对φChE的抑制作用大:其原因可能是由于AChE的磷酸化程度大于φChE。不同药剂对酶的最大抑制作用虽有所不同,但同一种药剂使两种酶受抑制的最高峰出现在同一时间,并且都在家蝇中毒昏迷时出现。 此外,AChE及φChE在被各种药剂在体内抑制后,经一定时间,出现恢复现象,但对于不同药剂,恢复出现的时间不同。恢复现象的产生,可能是由于酶的重新形成,或磷酸化酶的水解。 由体外抑制的结果(pI₅₀)与体内处理结果的比较,表明了体内外的抑制情况非常一致。     

竹红菌甲素对红细胞膜内脂双层的微扰

本文以荧光探针为手段,以人红细胞膜为材料,测量了膜偏振度的改变,荧光探针能量转移,荧光峰的蓝移和甲素激发峰的分裂。结果表明在有竹红菌甲素存在时,红细胞膜偏振度增加,探针荧光强度减小,荧光峰蓝移。甲素浓度增加时,上述现象更加明显,即它们之间有正的相关关系。同时,甲素激发光谱的a带发生分裂。据此,我们认为甲素对红细胞膜内脂双层产生明显微扰,甲素与红细胞膜间存在着相互作用。在甲素浓度较大时,它主要是渗入到红细胞膜脂双层的深层部位(膜脂肪酸链的12—16位)。     

高温对田间小菜蛾DNA损伤及4种抗药性相关酶系活性的抑制

研究了高温对福州上街菜田小菜蛾成虫4种抗药性相关酶系活性的影响。与饲养在25℃下的小菜蛾相比,33．5~C或40℃处理72h导致小菜蛾基因组DNA出现DNA凋亡特征梯度化条带。33~C饲养小菜蛾4、8、12或24h对小菜蛾成虫乙酰胆碱酯酶（AChE）和羧酸酯酶（CarE）活性无显著影响,但33℃饲养小菜蛾12或24h导致小菜蛾成虫谷胱甘肽s转移酶（GSTs）酶活性和细胞色素P450含量显著下降。36℃、24h可导致AChE活性显著下降,36℃、12h和24h可导致CarE活性显著下降,36℃、4h,8h,12h和24h可导致GST活性和细胞色素P450含量显著下降。总体上,高温对CarE、GSTs和细胞色素P450的抑制作用大于对AChE的影响,此外,3CC对AChE、CarE、GSTs酶活性和细胞色素P450含量的抑制作用大于33℃的抑制作用。     

Temperature effects on cholinesterases from rat brain capillaries

The activities of acetylcholinesterase (ACHE) and butyrylcholinesterase (BuChE) in rat brain capillaries were measured as a function of temperature. Arrhenius plots of the data revealed that AChE exhibits a biphasic Arrhenius plot with a distinct break (transition temperature) at about 15.2 kcal/mol. In contrast, BuChE did not show evidence of discontinuity. BuChE showed an activation energy higher than that of AChE in the physiological range of temperature. These data suggest a lack of lipid-protein interaction in the case of BuChE. Although the possibility exists that BuChE is weakly anchored to the membranes, our results indicate that BuChE is not bound, at least significantly, to cellular membranes in brain capillaries as is ACHE.     

Inherited and acquired interactions between ACHE and PON1 polymorphisms modulate plasma acetylcholinesterase and paraoxonase activities

The 5.5 Mb chromosome 7q21-22 ACHE/PON1 locus harbours the ACHE gene encoding the acetylcholine hydrolyzing, organophosphate (OP)-inhibitable acetylcholinesterase protein and the paraoxonase gene PON1, yielding the OP-hydrolyzing PON1 enzyme which also displays arylesterase activity. In search of inherited and acquired ACHE-PON1 interactions we genotyped seven polymorphic sites and determined the hydrolytic activities of the corresponding plasma enzymes and of the AChE-homologous butyrylcholinesetrase (BChE) in 157 healthy Israelis. AChE, arylesterase, BChE and paraoxonase activities in plasma displayed 5.4-, 6.5-, 7.2- and 15.5-fold variability, respectively, with genotype-specific differences between carriers of distinct compound polymorphisms. AChE, BChE and arylesterase but not paraoxonase activity increased with age, depending on leucine at PON1 position 55. In contrast, carriers of PON1 M55 displayed decreased arylesterase activity independent of the - 108 promoter polymorphism. Predicted structural consequences of the PON1 L55M substitution demonstrated spatial shifts in adjacent residues. Molecular modelling showed substrate interactions with the enzyme variants, explaining the changes in substrate specificity induced by the Q192R substitution. Intriguingly, PON1, but not BChE or arylesterase, activities displayed inverse association with AChE activity. Our findings demonstrate that polymorphism(s) in the adjacent PON1 and ACHE genes affect each other's expression, predicting for carriers of biochemically debilitating ACHE/PON1 polymorphisms adverse genome-environment interactions.     

Plant-parasitic Nematode Acetylcholinesterase Inhibition by Carbamate and Organophosphate Nematicides

The sensitivity of acetylcholinesterases (ACHE) isolated from the plant-parasitic nematodes Meloidogyne arenaria, M. incognita, and Heterodera glycines and the free-living nematode Caenorhabditis elegans to carbamate and organophosphate nematicides was examined. The AChE from plant-parasitic nematode species were more sensitive to carbamate inhibitors than was AChE from C. elegans, but response to the organophosphates was approximately equivalent. The sulfur-containing phosphate nematicides were poor inhibitors of nematode acetylcholinesterase, but treatment with an oxidizing agent greatly improved inhibition. Behavioral bioassays with living nematodes revealed a poor relationship between enzyme inhibition and expression of symptoms in live nematodes.     

Inhibition of erythrocyte acetylcholinesterase by n-butanol at high concentrations

Erythrocyte acetylcholinesterase (AChE) is bound to the membrane by a complex glycosylphosphatidylinositol anchor, so the effect of alcohol on AChE activity may reflect direct and/or membrane-mediated effects. The indication of a direct interaction between n-butanol and AChE molecules is the activation/inhibition of AChE by occupation of the enzyme's active and/or regulatory sites by alcohol. The activation of AChE can occur only at low concentrations of alcohols, while at high concentrations AChE is inhibited. In this work the mechanism of inhibition of erythrocyte AChE by n-butanol at high concentrations was studied. The values of activity, calculated assuming parabolic competitive inhibition, which implies that one or two molecules of inhibitor bind to the enzyme, fit well to the experimental values. From the values of the inhibition constants it was concluded that at high n-butanol concentrations two alcohol molecules usually interact with AChE.     

Modulation in Acetylcholinesterase of Rat Brain by Pyrethroids In Vivo and an In Vitro Kinetic Study

Abstract: The modulation in acetylcholinesterase (AChE) of rat brain by two pyrethroids—permethrin (PM) and cypermethrin (CPM)—was studied both in vivo and in vitro. PM inhibited AChE activity in all regions of the rat brain (cerebral cortex, cerebellum, corpora striata, brainstem, hippocampus, and hypothalamus) at 4, 8, and 12 h after gastric intubation, whereas CPM elevated the enzyme activity in vivo. Substrate-dependent enzyme kinetic studies have shown that PM and CPM behave as mixed-type inhibitors, as evidenced by alterations in both Michaelis-Menten constant ( K _m) and maximal velocity ( V _max) values. This indicates that both PM and CPM and substrate acetylcholine interact at hydrophobic subsites and may be able to bind simultaneously to the enzyme.     

Interaction of an organophosphate with a peripheral site on acetylcholinesterase

O-Ethyl S-[2-(diisopropylamino)ethyl] methylphosphonothioate (MPT) is an active site directed inhibitor of acetylcholinesterase (AChE). Inhibition of the Electrophorus electricus (G4) enzyme follows classical second-order kinetics. However, inhibition of total mouse skeletal muscle AChE and inhibition of the individual molecular forms from muscle, including the monomeric species, do not proceed as simple irreversible bimolecular reactions. Similarly, complex inhibition kinetics are observed for the purified enzyme from Torpedo californica. AChE can be cross-linked with glutaraldehyde into a semisolid matrix. Under these conditions the abnormal concentration dependence for MPT inhibition is accentuated, and a range of MPT concentrations can be found where inhibition of polymerized AChE is far less than that observed at lower concentrations. Inhibition in certain concentration ranges is partially reversible after removal of all unbound ligand. Thus, there are two different modes of organophosphorus inhibition by MPT: the classical irreversible phosphorylation of the active site and a reversible interaction at a site peripheral to the active center. Propidium, a well-studied peripheral site ligand, can prevent the later interaction. Hence, the second site of MPT interaction with AChE may overlap or be linked to the peripheral anionic site of AChE characterized by the binding of propidium and other peripheral site inhibitors.     

Characterization of "fetal-type" acetylcholinesterase in hemin-treated K562 cell culture

The alteration of acetylcholinesterase (ACHE) activity, a marker enzyme of erythroid differentiation, was studied during the hemin-induced erythroid differentiation of K562 human leukemia cells in suspension culture. The kinetics of postinduction differentiation was followed by determining the hemoglobin (Hb) content and the ACHE activity of cells. Embryonic hemoglobins as well as small quantities of fetal Hb (HbF) were synthetized by stimulated cells. The peaks of ACHE activity preceded the highest level of Hb content and, following induction, reached their pinnacles at 72 and 120 hours, respectively. These data indicate that ACHE activity is an earlier and more sensitive marker for hemin-induced erythroid differentiation of K562 cells than is elevated Hb content. Electrophoretic mobility of ACHE from hemin-treated cells proved to be the fetal type, but after incubation with neuraminidase, the rate of migration decreased to the level of the adult type enzyme.