| The objects of the study were to compare the biochemical characteristics of AChE between adult honeybees of Apis cerana cerana Fabricius and Apis mellifera ligustica Spinola. Partial purification was conducted by several procedures. The results were as follows:1 The effects of AChE concentration, substrate (ATCh) concentration, pH of the reaction system, the reaction temperature and the reaction time on the assay of the specific activity of AChE from the head of Apis mellifera ligustica Spinola were studied by orthogonal matrix methods. L75 (56) orthogonal matrix was adopted, without considering interaction. The results revealed that temperature of the reaction system was the most important factor for measuring the activity of AChE from honeybee heads, and the other four factors also affected it remarkably (P<0.01 ). The effects on the activity of AChE were in the order of temperature > pH > time > concentration of AChE > concentration of the substrate. The optimal conditions of assaying the activity of AChE from honeybee heads were determined by range analysis, analysis of variance and multiple comparison, which were 0.2 heads/ mL, 0.8 mmol/ L substrate, pH 7.5, 40°C, and 5 minutes.2 Body distribution and subcelullar distributions of AChE from both honeybees were investigated. The results showed that AChE was distributed mostly in the heads of A. cerana cerana and A. mellifera ligustica, in which the percentages were 65 % and 65.7 %, respectively. There were no differences (P>0.05) in the distribution percentages of AChE in head and abdomen from these two honeybees, but there was a significant difference (p<0.01) in thorax, in which the distribution percentage of AChE from A. cerana cerana was significantly higher than that from A. mellifera ligustica (P<0.01). The subcelluar distributions of AChE in both honeybees hadsimilar tendency. The major portion of the total AChE was member-bound (above 90 % in mitochondria, microsoine, nucleus and cell debris) and associated primarily with mitochondria (60 % in A. cerana cerana and 70 % in A. mellifera ligustica).3 The substrate specificities of ACliEs from the head of two honeybees were studied using acetylthiocholine iodide (ATCh), acetyl- ([3-methyl) thiocholine (MeTCh), s-propionylthiocholine (PrTCIi) and s-butyrylthiocholine iodide (BuTCh) as substrates, respectively. The rank order from the highest affinity to the lowest was PrTCIi > BuTCh > ATCh > MeTCh as indicated by Km values in A. cerana cerana; however, in A. mellifera ligustica it was BuTCh > PrTCh > ATCh > MeTCh, which was different from that in A. mellifera liguslica. The rank order for hydrolyzing efficiency, however, was MeTCh> ATCh>PrTCh> BuTCh in A. cerana cerana as indicated by K,liax values; and in A. mellifera ligustica the order was ATCh> MeTCh> PrTCh> BuTCh. There was no statistical difference in AChE affinities toward the four substrates between A. cerana cerana and A. mellifera liguslica based on comparison of the Michaelis constant (Km) values (Z^O.05). However, the hydrolyzing efficiency of AChE from A. mellifera liguslica for four substrates was significantly higher than that from A. cerana cerana (P<0.0\).4 The inhibition time-course curve showed that both honeybees were sensitive to the tested inhibitors. Among the tested inhibitors, eserine was the most potential inhibitor to AChEs of both bees. The bimolecular reaction constant (K\) indicated that AChE from A. mellifera ligustica was significantly (P<0.05) or extremely significantly (P<0.0\) more sensitive to eserine, propoxur, thiodicarb and carbofuran than that from A. cerana cerana. However, methomyl was a more powerful inhibitor to A. cerana cerana than to A. mellifera ligustica. The determination of recovery rate of inhibition (K"3) by carbamate suggested that AChEs from both honeybees can reactivate naturally. When inhibited by propoxur and thiodicarb, the recovery rate of...
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