Ando M, Wakamatsu K
J Toxicol Sci. 1982 Aug;7(3):185-92. doi: 10.2131/jts.7.185.
The Lineweaver-Burk plot of the activity of human serum cholinesterase against the concentration of butyrylthiocholineiodide was shown by two intersecting lines. The Hill plot of cholinesterase activity was linear over the entire range of the substrate concentration. The n value, an interaction coefficient, was less than 1.0 (about 0.8). These results suggest that cholinesterase has multiple substrate binding sites. Acephate, one of the organophosphorous insecticides, inhibited the activity of cholinesterase. Acephate at concentration under 1.25 mM (about 230 ppm in serum) did not inhibit the activity of cholinesterase. The minimum concentration of acephate inhibition of cholinesterase activity was at 2.5 mM. An equilibrium constant(K) can be used as an indicator of inhibitory effect on cholinesterase. The serum cholinesterase activity of workers who were exposed to acephate is not affected when the concentration of acephate in serum is less than 200 ppm. This result suggests that the activity of serum cholinesterase is not an accurate indicator of the exposure of the low toxic insecticides, e.g. acephate. The inhibitory effect of acephate on cholinesterase decreased after the incubation with S-9 mixture. This result suggests that a part of acephate is metabolized to inactive substances in the liver.
人血清胆碱酯酶活性相对于丁酰硫代胆碱碘化物浓度的Lineweaver-Burk图由两条相交线表示。胆碱酯酶活性的Hill图在底物浓度的整个范围内呈线性。n值（一种相互作用系数）小于1.0（约为0.8）。这些结果表明胆碱酯酶具有多个底物结合位点。乙酰甲胺磷是有机磷杀虫剂之一，它抑制胆碱酯酶的活性。浓度低于1.25 mM（血清中约230 ppm）的乙酰甲胺磷不抑制胆碱酯酶的活性。抑制胆碱酯酶活性的乙酰甲胺磷的最低浓度为2.5 mM。平衡常数（K）可作为对胆碱酯酶抑制作用的指标。当血清中乙酰甲胺磷的浓度低于200 ppm时，接触乙酰甲胺磷的工人的血清胆碱酯酶活性不受影响。该结果表明血清胆碱酯酶活性不是低毒杀虫剂（如乙酰甲胺磷）暴露的准确指标。与S-9混合物孵育后，乙酰甲胺磷对胆碱酯酶的抑制作用降低。该结果表明乙酰甲胺磷的一部分在肝脏中代谢为无活性物质。
