BCHE基因复合杂合突变致先天性丁酰胆碱酯酶缺乏症一例

丁酰胆碱酯酶是一种丝氨酸水解酶,可催化胆碱酯类的水解,包括肌肉松弛剂琥珀酰胆碱和米伐库铵。丁酰胆碱酯酶缺乏可能导致麻醉后呼吸暂停。先天性丁酰胆碱酯酶缺乏症是由于位于3号染色体（3q26.1）上的BCHE基因突变引起,多位点的复合杂合突变可能致病。     

浙江产眼镜蛇蛇毒胆碱酯酶的研究 Ⅱ.酶学性质与生物毒性

浙江产眼镜蛇蛇毒胆碱酯酶具有乙酰胆碱酯酶的特征,有以下几点事实:1.乙酰胆碱酯是酶的最适底物;2.过量底物抑制酶活性;3.BW_(62)C_(47)、BW_(284)C_(51)是典型的真性胆碱酯酶抑制剂,对蛇毒胆碱酯酶也同样具有抑制作用。     

胆碱酯酶抑制剂对化学性糖尿病影响的实验研究

目的：探讨胆碱酯酶抑制剂对化学性糖尿病的影响。方法：用胆碱酯酶抑制剂溴化斯的明对四氧嘧啶所致糖尿病家兔进行治疗观察。结果：仅给予溴化斯的明治疗后，血清胆碱酯酶活性、空腹血糖（FBG）、糖化血红蛋白（GHB）显著下降，而血清胰岛素（insulin）水平明显升高。结论：血清胆碱酯酶抑制剂可以促进胰岛素的分泌，降低空腹血糖和糖化血红蛋白。     

Pro167位点突变型CTX-M-14超广谱β-内酰胺酶的动力学特征

目的 对Pr0167位点突变型CTX-M-14超广谱β-内酰胺酶(ESBL)的动力学特征进行分析与评价.方法 以携带CTX-M-14基因的大肠埃希菌临床株为模板,克隆目的 基因,重组工程菌,并表达CTX-M-14型ESBL.进而采用基于重叠延伸PCR法的定点突变技术,将CTX-M-14型ESBL的167位点Pro(P)分别突变为Gly(G)、Gln(Q)、Ser(S)和Thr(T),重组构建P167G、P167Q、P167S和P167T四株突变型的CTX-M-14工程菌.表达与纯化野生型、重组型和突变型CTX-M-14型ESBL,检测其水解β-内酰胺类抗菌素的酶动力学参数(Kcat、Km和Km).结果 对野生型与重组型CTX-M-14型ESBL的酶动力学参数进行配对t检验,结果显示两者Kcat(t=1.796,P=0.123)、Km(t=0.559,P=0.596)、Kcat/Km(t=0.893,P=0.406)间的差异无统计学意义(P>0.1).与重组CTX-M-14型ESBL相比,P167S突变型酶对头孢他啶的Km值大幅降低,为突变前的1/16(8.39/134.85);Kcat和Km值分别为突变前的2.87倍(1.81/0.63)和43.6倍(0.218/0.005);且对青霉素、氨苄西林、头孢唑啉、头孢呋辛、头孢曲松和头孢噻肟的Kcat/Km值都呈现出显著减小的趋势(P<0.05).与重组CTX-M-14 ESBL相比,P167Q和P167G突变型酶对头孢他啶的Kcat值亦大幅减小(P<0.01),而P167T突变型对头孢他啶的酶动力学参数无明显变化.结论 重组型与野生型CTX-M-14 ESBL之间各项酶动力学参数的差异无统计学意义(P>0.1).而P167S位点的突变,不仅增强了CTX-M-14型ESBL对头孢他啶的亲和力,也加快了酶-底物复合物的转换速率.通过对Pr0167位点4种突变型酶的动力学参数比较,初步说明突变型CTX-M ESBL对头孢他啶所具备的高水解活性机制,不能简单地归结于Pro167位点被小侧链氨基酸残基取代而导致酶活性中心空间扩大的解释.

Abstract：

Objective To analyze and evaluate the characteristics of enzyme kinetics of CTX-M-14 type extended-spectrum β-lactamase(ESBL) with Pro167 residue substitution. Methods By molecular cloning and PCR techniques, CTX-M-14 gene was directionally cloned into plasmid pET28a( + ) from a clinical E. coli isolate and formed an expression vector to transform competent E. coli BL21 (DE3 ). Prol67 residue substitutions of P167G, P167Q, P167S and P167T were introduced to CTX-M-14 by site-directed muta-genesis based on overlap extension PCR with the former recombinant plasmid as PCR template, respectively.The wild-type CTX-M-14, recombinant CTX-M-14 protein and its variants were expressed and purified, then their steady-state kinetic parameters (Kcat, Km and Kcat/Km ) against β-lactam antibiotics were determined.Results The kinetic parameters of wild-type and recombinant CTX-M-14 had no statistically significant differences (P>0.1). The 1/Km, Kcat and Kcat/Km values of P167S variant against ceftazidime were 16-fold, 2.87-fold and 43.6-fold higher than those of recombinant CTX-M-14, respectively, and the Kcat/Km value of P167S variant against penicillin, ampicillin, cefazolin, cefuroxime, ceftriaxone, cefotaxime decreased( < 0.05). Compared with the kinetic parameters of recombinant CTX-M-14, the kinetic parameters of P167T variant against ceftazidime had no significant change, but the Kcat values of P167Q and P167G variants decreased dramatically(P<0.01). Conclusion There was no difference between the enzyme activities of wild-type and recombinant CTX-M-14. P167S variant could not only promote the enzyme affinity of CTX-M-14 to ceftazidime but also improve the conversion rate of enzyme-substrate complex in the ceftazidime hydrolysis. The comparison of the kinetic parameters of CTX-M-14 and its variants with Pro167 residue substitution showed that the increased activity of CTX-M ESBL variants against ceftazidime could not be simply explained with the enlarged cavity in active site that may be caused by the replacement of Pro167 residue by smaller amino acids.     

腺病毒E1A蛋白对大鼠肺泡上皮细胞谷胱甘肽活性的影响及其机制探讨

目的 研究腺病毒E1A蛋白潜伏感染对大鼠肺泡上皮细胞谷胱甘肽(GSH)活性的影响及其机制.方法 构建稳定表达腺病毒E1A蛋白的大鼠肺泡上皮细胞,观察氧化剂刺激时细胞内GSH含量变化,检测GSH合成限速酶γ-谷氨酰半胱氨酸合成酶(γ-GCS)催化活性的变化,通过观察γ-GCS 催化亚单位(GCLC)基因蛋白表达水平、mRNA表达水平和5′-上游调控序列调控的荧光素酶活性的改变,了解影响酶活性改变的机制.结果 腺病毒E1A蛋白表达抑制氧化应激时GSH的合成,抑制γ-GCS 催化活性和蛋白表达水平,抑制GCLC 基因mRNA表达,与5′-上游调控序列报导系统获得的结果一致.结论 腺病毒潜伏感染可能通过抑制GCLC基因 5′-上游调控序列的促转录活性,抑制了γ-GCS的表达和催化活性,从而抑制了氧化应激时GSH的合成,削弱机体的抗氧化作用,加重氧化损伤,可能是腺病毒潜伏感染参与慢性阻塞性肺病(COPD)发病的机制之一.     

脊髓—肌肉联合培养时神经肌肉接头发生的形态学观察

联合培养分离的小鼠胚胎脊髓与肌肉小块时,能够形成神经肌肉接头。培养第7天时,肌管被小球状的神经末梢支配,神经与肌管的接触处,未显胆碱酯酶活性;第14天时,神经纤维发出侧支,神经末梢除球状外还有简单的树枝状者。该期内,终板胆碱酯酶活性开始检出。肌纤维呈现多处神经接触,或者数根轴突支配于同一处,形成“混合接触”。胆碱酯酶活性只能检出多个接触中的一个,“混合接触”未能显示酶的活性;第21天时,终板数目和胆碱酯酶活性均显著增加;第30天后,终板的形态结构和酶活性强度与在体幼年小鼠的终板相似。这些终板都为单神经支配。当脊髓和肌肉联合培养时,肌纤维的分化,依赖于运动神经的支配;另一方面,神经元的生长和存活,与肌肉纤维的存在也密切相关。     

绿豆胰蛋白酶抑制剂两活性区域的拆分

绿豆胰蛋白酶抑制剂是一小分子蛋白质,具有两个活性区域,可以同时抑制两分子胰蛋白酶。用苯乙二醛及顺丁烯二酸酐分别进行化学修饰,都可使其活力降至原有的50％左右,表明此两活性中心分别应为精氨酸残基及赖氨酸残基。绿豆抑制剂经胃蛋白酶酶解后,活力不丧失,在凝胶过滤中出现分子量为原抑制剂一半的新活力峰,经证实为两个不同活性中心的活力碎片。利用两活     

泛素依赖的蛋白酶体水解通路对p53转录活性的作用

目的　探讨 p5 3的转录过程与其泛素调节的蛋白降解途径的相互关系。方法　采用瞬时转染报告基因测定法 ,测定细胞裂解液荧光素酶活性 (p5 3的转录活性 )或Western -blot、免疫共沉淀测定细胞内 p5 3蛋白水平。结果　删除 p5 3N末端 1- 19个氨基酸 (mdm2结合位点 ) ,可显著减少 p5 3的转录活性 ,提示p5 3的降解片段不能与其转录活性片段相分离。特异性蛋白酶体抑制剂存在时 ,细胞内 p5 3稳态蛋白水平升高 ,而 p5 3的转录活性受到显著的抑制。UBA酶 (ubiquitin -activatingenzyme)失活 ,导致p5 3转录功能降低。结论　p5 3的蛋白水解途径对其转录反应是必须的     

长角血蜱唾液腺Apyrase的生物学特性和功能的研究

长角血蜱在吸血时 ,其唾液腺中的 apyrase可明显地抑制由 A DP所诱导的血小板聚集反应 ,并呈剂量反应关系 ,1/ 2对唾液腺可以完全抑制血小板的聚集反应。通过 apyrase的动力学、 HPLC分子筛、等电聚焦电泳和温度敏感性实验证明 ,水解 ATP和 ADP并不是 ATP酶、 ADP酶或几种酶共同作用的结果 ,而是一种酶即 apyrase的作用结果。Apyrase对 Ca2 具有依赖性。而 Mg2 、Zn2 、Mn2 对之影响较小 ,Hg2 和EDTA是 apyrase的抑制剂。吸血对蜱唾液腺 apyrase活性影响较大 ,吸血 6天时其活性最大 ,吸血后活力明显下降。A pyrase与哺乳动物的 5′-核苷酸酶相似 ,它是一种糖基 -磷脂酰肌醇 ( GPI)膜锚结构蛋白。     

结核分枝杆菌FtsZ抑制剂的筛选和活性研究

目的筛选结核分枝杆菌FtsZ的特异性抑制剂,为抗结核药物的研发提供先导化合物。方法应用本实验室已经建立的结核分枝杆菌FtsZ抑制剂筛选模型对化合物库进行筛选,获得能够抑制FtsZ的化合物202E,对其进行IC50以及分子水平活性测定,并利用DS 4.0软件将化合物202E与FtsZ的活性位点进行对接。结果化合物202E能够抑制结核分枝杆菌FtsZ的GTP酶活性,其IC50为15.46μmol/L。202E还能够抑制FtsZ蛋白的聚合。通过分子对接,发现202E能够与FtsZ的GTP结合位点结合,抑制FtsZ的GTP酶活性。结论化合物202E是活性较好的结核分枝杆菌FtsZ抑制剂。     

Catalytic antibodies with acetylcholinesterase activity

We describe three catalytic cholinesterase-like catalytic antibodies (Ab1), as well as anti-idiotypic (Ab2) and idiotypic (Ab3) antibodies, to one of the Ab1s. The Ab1s were raised against the human erythrocyte acetylcholinesterase (AChE), and are unusual in that they both recognise and resemble acetylcholinesterase in their catalytic activity. No contamination of the antibody preparations with either acetylcholinesterase or butyrylcholinesterase (BChE) was found. None of the Ab2s showed catalytic activity, whereas four Ab3s did (an incidence of 1.26% of all Ab3s). Although there is considerable resemblance between Ab1s and Ab3s, there are significant differences between the two groups. All the antibodies were inhibited by phenylmethylsulphonyl fluoride (PMSF), indicating the presence of a serine residue in their active sites, and were inhibited by the cholinesterase active site inhibitors iso-OMPA and pyridostigmine, suggesting the similarity of the sites to those of cholinesterases. The Ab3s resemble the Ab1s in their ability to hydrolyse both acetyl and butyrylthiocholine (BTCh). However, the Ab3s appear to be better catalysts, having significantly reduced K(m) values (for acetyl, but not for butyrylthiocholine) and increased turnover numbers (K(cat)), rate enhancements (K(cat)/K(uncat)) and K(cat)/K(m) ratios, for both substrates, although these values by no means approach those of the natural enzymes. The Ab1s appear to have structures resembling the anionic sites of cholinesterases, as shown by their reaction with the anionic site inhibitors (edrophonium and tetramethylammonium). No such reactions were observed in the Ab3s. None of the antibodies show evidence of the sites resembling the peripheral anionic site (PAS) of acetylcholinesterase. All the antibodies recognise, to varying degrees, the peripheral anionic site of acetylcholinesterase. This was shown by their ability to inhibit acetylcholinesterase, to compete with peripheral site inhibitors, and to block acetylcholinesterase-mediated cell adhesion, a property of this site. The results indicate idiotypic mimicry of a catalytic antibody's active site, and suggest that the development of the catalytic activity in the anti-acetylcholinesterase antibodies may be related to the structural features of the peripheral anionic site of acetylcholinesterase.     

Cholinesterase-like catalytic antibodies: reaction with substrates and inhibitors

We have previously described a catalytic monoclonal antibody, raised against acetylcholinesterase (AChE) and capable of hydrolysing acetylthiocholine. Here, we describe two more such antibodies. All three antibodies were raised against the same antigen, human erythrocyte AChE, a commercial product purified using the cholinesterase anionic site inhibitor, tetramethylammonium. IgG was purified on Protein A-Sepharose, and lack of contamination with AChE or butyrylcholinesterase (BChE) was demonstrated on sucrose density gradients and immunoassay of the fractions. The antibodies recognised AchE and were capable of hydrolysing acetylthiocholine and the larger butyrylthiocholine substrate, and were inactivated by phenylmethylsulphonyl fluoride (PMSF), indicating a serine residue in the active site. K(m), K(cat), K(cat)/K(uncat) and K(cat)/K(m) values were obtained for both substrates. The active sites of the antibodies were probed with anti-cholinesterases known to react with the active and anionic sites of acetyl- and BChE, and the peripheral anionic site of AChE. The antibodies were inactivated to varying degrees by the BChE inhibitors iso-OMPA, ethopropazine and tetracaine, indicating a less sterically constrained site than AChE and the lack of an acyl-binding pocket. They were also partially inhibited by the AChE-specific inhibitors, BW284c51 and propidium. No peripheral anionic site, as seen in AChE, was observed, shown by the almost complete lack of reaction with fasciculin. All three antibodies appear to have structures resembling the anionic sites of the cholinesterases, seen by their inhibition by quaternary and tricyclic compounds. Further work is required to determine whether the catalytic activity shown by these antibodies is germline-encoded, or is the result of complexation of the antigen with an inhibitor at a peripheral site.     

Idiotypic mimicry of a catalytic antibody active site

We have previously described three catalytic antibodies (Ab1s) raised against human erythrocyte acetylcholinesterase (AChE). These antibodies both recognise and resemble AChE in their reaction with substrates and appear with a relatively high frequency. We do not know, however, why catalytic activity should have developed in response to a ground state antigen. This question has implication for autoimmune disorders, which are frequently characterised by the presence of catalytic antibodies, many of which have cytotoxic effects. In this study, we raised anti-idiotypic (Ab2) and anti-anti-idiotypic (Ab3) antibodies to a catalytic Ab1 and examined their properties. None of the Ab2s showed catalytic activity, whereas four of the Ab3s did, an incidence of 1.26%. No contamination of antibody preparations with either AChE or butyrylcholinesterase (BChE) was found. Immunisation of mice with AChE, as well as AChE complexed with various inhibitors, resulted in a significant increase in catalytic immunoglobulins in the serum, compared with non-immunised mice and mice immunised with the Ab1. There appears to be considerable resemblance between Ab1s and Ab3s, but there are also significant differences between the two groups. All the antibodies were inhibited by phenylmethylsulphonyl fluoride (PMSF), indicating the presence of a serine residue in their active sites and were inhibited by the cholinesterase active site inhibitors tetraisopropyl pyrophosphoramide (iso-OMPA) and pyridostigmine. The Ab3s resembled the Ab1s in their ability to hydrolyse both acetylthiocholine (ATCh) and butyrylthiocholine (BTCh). However, the Ab3s appear to be better catalysts, having significantly reduced K(M) values (for ATCh but not BTCh) and increased turnover numbers (K(cat)), rate enhancements (K(cat)/K(uncat)) and K(cat)/K(M) ratios. The Ab3s also had reduced affinities for cholinesterase anionic site inhibitors (edrophonium, tetramethylammonium and BW284c51) and no affinity at all for the AChE peripheral anionic site (PAS) inhibitor fasciculin. All the antibodies recognise, to some degree, the PAS of AChE, shown by their ability to inhibit AChE, to compete with peripheral site inhibitors and to block AChE-mediated cell adhesion, a property of the site. These results indicate idiotypic mimicry of the catalytic antibody's active site, suggesting that the catalytic activity is due to affinity maturation of immunoglobulin genes in response to a specific antigen, namely, the PAS of AChE. Further studies are required to determine the structural features of this ground state antigen responsible for the development of catalytic activity.     

Anti-acetylcholinesterase antibodies display cholinesterase-like activity

A monoclonal antibody (mAb) raised against human acetylcholinesterase (AChE) was found to have catalytic activity. A similar phenomenon was observed in a polyclonal antibody raised against the same antigen. The antibodies were demonstrated to be pure, and no contamination with either AChE or butyryl-cholinesterase was found. Both antibodies hydrolyzed acetylthiocholine, an AChE substrate, and the mAb followed Michaelis-Menten kinetics. Six other mAb and one other polyclonal antibody showed no evidence of catalytic activity. This development of cholinesterase-like behavior by certain anti-AChE antibodies may have arisen by stable complexation of the enzyme with a substrate or inhibitor during antigen presentation. This phenomenon may have implications for the diagnostic measurement of AChE activity as well as in assessing the immunological reasons for the markedly raised AChE level in developmental conditions such as Hirschsprung's disease.     

Characterization of a monoclonal antibody against P57, the C3/C3b-cleaving proteinase expressed in human erythrocyte membranes

A monoclonal antibody was raised against p57, a serine proteinase, characterized by an apparent molecular weight of 57 kDa, and purified from human erythrocyte membranes. P57 proteinase cleaves the human third component of complement, C3. The antibody selected, MP1, of IgG2a isotype, precipitated specifically the p57 antigen which carried the C3/C3b-cleaving activity present in membrane crude extract of human erythrocytes. P57 proteinase eluted from MP1-sepharose was inhibited by 5 x 10(-4) M PMSF, enhanced by 0.5% SDS and generated C3 fragments identical to those generated by membrane crude extract of human erythrocytes. All these properties were identical to those of the p57 previously purified by biochemical procedures. In addition, 5000 binding sites were detected on cell surface. This MP1 monoclonal antibody will be helpful to analyse the role of p57 in human erythrocytes.     

An iron regulatory-like protein expressed in Plasmodium falciparum displays aconitase activity

Plasmodium falciparum iron regulatory-like protein (PfIRPa) has homology to both mammalian iron regulatory proteins and aconitases and is capable of binding RNA iron response elements. We examined the subcellular localization of PfIRPa and its enzymatic properties at low oxygen tension. Differential digitonin permeabilization of isolated trophozoites with subsequent Western blot analysis suggests that the localization of PfIRPa is predominantly in the membranous compartments of the parasite, such as the mitochondrion. Immunofluorescence analysis showed that PfIRPa colocalizes with heat shock protein 60 (Hsp60), a mitochondrial marker, and is also present in the parasitic cytosol/food vacuole. Under conditions favoring the formation of an iron-sulfur cluster, recombinant PfIRPa (rPfIRPa) had aconitase activity as detected by a colorimetric NADPH-MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) assay. As assessed by the hydration of cis-aconitate spectrophotometrically at 240 nm, rPfIRPa had high affinity for cis-aconitate (Km=3.5 microM) but a low turnover number (Kcat= 3.3 s(-1)). The overall catalytic efficiency (Kcat/Km) of rPfIRPa was similar in magnitude to human cytosolic IRP1/aconitase and human mitochondrial aconitase. PfIRPa immunoprecipitated from parasite lysates also had aconitase activity, as assessed by an MTT-based assay. Our results provide evidence that PfIRPa localizes in the mitochondrion and in the cytosol/food vacuole and is able to demonstrate aconitase activity. Further understanding of the role of PfIRPa/aconitase in the regulation of P. falciparum homeostasis may contribute towards the development of novel antimalarial strategies against plasmodial species.     

Generation of a monoclonal antibody against facteur thymique serique (FTS).

A monoclonal antibody against one of the thymic hormones, facteur thymique serique (FTS), was generated by hybridization between mouse NS-1 myeloma cells and BALB/c splenocytes, the latter obtained from BALB/c mice immunized with synthetic FTS coupled to mouse IgG. Enzyme-linked immunosorbent assay (ELISA) was developed and employed to detect the hybridoma secreting specific antibody. The monoclonal antibody (MA-FTS) was highly specific for FTS and did not cross-react with other thymic hormones or other unrelated peptides. MA-FTS could recognize FTS (or FTS-like molecule) in human serum and could absorb completely the FTS-like activity from human serum.     

Distribution of neutral endopeptidase activity in human blood leukocytes

We investigated the distribution of neutral endopeptidase (NEP; EC 3.4.24.11) activity, a possible regulatory enzyme for neuropeptide-induced leukocyte activations, in each cell type of human blood leukocytes. The NEP activity assessed by an NEP inhibitor phosphoramidon-sensitive Met5-enkephalin degrading activity was present in neutrophils and the common acute lymphoblastic leukemia antigen (CALLA)-positive leukemic cells (59 pmol/min/10(6) cells and 62 pmol/min/10(6) cells, respectively); however, the NEP activity was virtually absent in lymphocytes, monocytes, eosinophils, basophils, CALLA-negative leukemic cells, or a promyelocytic cell line HL-60. The enzymatic activity was characterized as NEP on the basis of the values of kinetic parameters (Km = 61 microM, Kcat = 1,692 min-1, and Kcat/Km = 28 min-1 microM-1) and the values of IC50 of two NEP inhibitors phosphoramidon and thiorphan (7.4 nM and 8.4 nM, respectively). The distribution of NEP detected immunocytochemically using anti-NEP monoclonal antibodies was also found to be parallel with the distribution of NEP activity among peripheral blood leukocytes.     

Human complement (C3b) receptors defined by a mouse monoclonal antibody.

The aim of the present study was to prepare a monoclonal antibody against human C3 receptors. The monoclonal antibody termed C3RTo5, which is characterized in this study, inhibited the ligand binding of C3b receptors of human erythrocytes, neutrophils and lymphocytes, but did not block the ligand binding of C3bi and C3d receptors. C3RTo5 reacted only with cells that express C3b receptors. It did not react with cells that do not express C3 receptors or with cells that express C3 receptors other than C3b receptors. The reactivity of C3RT05 against C3b receptors of human erythrocytes, neutrophils, glomerular cells, tonsil cells, or spleen cells could be removed by absorption with human erythrocytes or tonsil cells, whereas absorption with human peripheral T cells or sheep erythrocytes had no effect. In immunoprecipitation studies, a glycoprotein with a mol. wt of 205,000 could be isolated with C3RTo5 from non-ionic detergent lysate of tritiated tonsil cells. A rabbit antiserum prepared against this glycoprotein was able to stain C3b receptor-positive cells, inhibit C3b receptor ligand-binding activity and, furthermore, to precipitate a 205,000 mol. wt component. The results of this study indicate that C3RTo5 is a monoclonal antibody with selective reactivity to C3b receptors and presumably to the binding sites within the receptor molecule. Using C3RTo5 further strong evidence was obtained that membrane-bound C3b receptors have a mol. wt of 205,000.