芳胺和脂环仲胺的N-乙酰化

芳胺和脂环仲胺与乙酸铵在乙酸中回流反应，得到N-乙酰化产物。18例收率中至优。邻氯（硝基）苯胺不反应。其它吸电子基团取代的苯胺乙酰化收率降低。     

尿中异烟肼的乙酰化分型方法比较

尿中异烟肼的乙酰化分型方法比较宋景平季永平王硕刘若曼北京市劳动卫生职业病防治研究所（１０００２０）Ｎ－乙酰化转移酶是体内药物代谢和化学物质转化的重要酶类。测定乙酰化分型就可得知酶的活性。Ｎ－乙酰化代谢型的测定对指导临床合理用药和研究芳香胺类毒物与职业...     

N-乙酰转移酶的多态性及其对肿瘤风险性的影响

N-乙酰转移酶是Ⅱ相药物代谢酶,在人体内由两个不同的基因编码,产生两个同酶NAT1和NAT2。NAT2的表达具有多态性,其慢乙酰化表型为NAT2基因编码区点突变所致。NAT1亦具有基因结构上的变异,不同的突变等位基因其酶表达水平不同。生化学研究表明NAT1和NAT2在致癌物质的代谢激活或灭活过程中起重要作用。流行病学研究则提示NATs的多态性与某些肿瘤的风险性有关,代谢基因型/表现型将通过影响DNA结合物的水平进而影响肿瘤的发生。如果肿瘤的遗传易感性这一生物标记能够成功地建立起来,将有助于更好地预防和控制人类疾病。     

芳香叠氮化物还原为胺

芳香叠氮化物在自由基引发剂1，1’-偶氮二环己腈（ACCN）和催化量叔十二烷硫醇存在下，经三乙基硅烷还原为相应的芳胺。除含取代基为硝基、溴、碘之外，18例收率基本定量。     

N-乙酰基转移酶2基因多态性与柳氮磺吡啶药物效应的相关性

<正>N-乙酰基转移酶2(N-acetyltransferase 2,NAT2)是柳氮磺吡啶(sulfasalazine,SASP)在人体内乙酰化代谢的关键酶。NAT2基因编码区的单核苷酸多态性可以造成氨基酸序列变化,进而影响酶含量[1]或活性[2],并对相关药物的代谢产生影响。近年来,NAT2编码基因的多态性与SASP药物效应的相关性备受关注,现将目前的研究进展综述如下。     

GC-MS法测定药用复合膜中25种初级芳香胺的迁移量

目的:采用GC-MS法完成对药用复合膜中25种芳香胺迁移量的测定.方法:采用GC-MS法,经过固相萃取前处理技术,对25种芳香胺对照品进行定性定量分析,确定定性、定量离子及保留时间,完成对药用复合膜样品中25种芳香胺迁移量的测定.结果:25种芳香胺的检出限在0.026 7～1.062 7μg之间;重复性相对标准偏差(R...     

芳香药用植物的抗氧化活性成分及其药理作用研究进展

目的我国芳香药用植物资源丰富,种类繁多,应用广泛。芳香药用植物因兼具芳香植物与药用植物2个类群的属性,成为国内外的研究热点,而具有抗氧化性质的芳香药用植物更是成为合成抗氧化剂的最佳潜在替代品。本文综述了近年来国内外芳香药用植物在抗氧化活性成分和药理作用方面的研究,并对芳香药用植物资源的充分利用与进一步研究进行展望,旨在为具有抗氧化活性的芳香药用植物在食品、药品、保健品和化妆品等方面的应用提供一定的理论依据。     

N-羟乙基酰胺类组蛋白去乙酰化酶抑制剂的设计、合成及活性评价

目的为了降低传统异羟肟酸类组蛋白去乙酰化酶抑制剂的毒副作用和改善体内代谢快的缺点,本课题组设计并合成了具有新型锌离子螯合基团的一类化合物,并测定了其对肿瘤细胞的抑制活性。方法以取代苯甲酸、6-氨基己酸等作为原料合成目标化合物。采用MTT法检测目标化合物的细胞毒性,并通过酶抑制实验进一步检测化合物的活性。结果化合物a1~a4对肿瘤细胞的抑制作用较SAHA弱(P<0.05),化合物a5~a6对A549细胞抑制作用与阳性对照SAHA相当,并且均具有较好的酶抑制作用,与MTT结果基本一致。结论此类具有新型锌离子螯合集团的组蛋白去乙酰化酶抑制剂具有较好的抗肿瘤活性和抑酶活性,具有进一步研究的价值。     

组蛋白去乙酰化酶抑制剂的研究进展

表观遗传学是目前遗传学研究的热点,而肿瘤的发生与表观遗传学关系密切.表观遗传修饰中组蛋白乙酰化酶(HAT)和组蛋白去乙酰化酶(HDAC)之间的动态平衡控制着染色质结构和基因表达.HDAC抑制剂作为新一代潜在靶向抗肿瘤药物,为国内外药学研究的热点.本文综述HDAC抑制剂的作用机制及临床研究进展.     

Eukaryotic arylamine N-acetyltransferase. Investigation of substrate specificity by high-throughput screening

Arylamine N-acetyltransferases (NAT; EC 2.3.1.5) catalyse the transfer of acetyl groups from acetylCoA to xenobiotics, including drugs and carcinogens. The enzyme is found extensively in both eukaryotes and prokaryotes, yet the endogenous roles of NATs are still unclear. In order to study the properties of eukaryotic NATs, high-throughput substrate and inhibitor screens have been developed using pure soluble recombinant Syrian hamster NAT2 (shNAT2) protein. The assay can be used with a wide range of compounds and was used to determine substrate specificity of shNAT2. We describe the expression and characterisation of shNAT2 and also purified recombinant human NAT1 and NAT2, including the use of the assay to explore the substrate specificities of each of the enzymes. Hamster NAT2 has similar substrate specificity to human NAT1, acetylating para-aminobenzoate but not arylhydrazine and hydralazine compounds. The overlapping but distinct substrate-specific activity profiles of human NAT1 and NAT2 were clearly observed from the screen. Naturally occurring compounds were tested as substrates or inhibitors of shNAT2 and succinylCoA was found to be a potent inhibitor of shNAT2.     

Inactivation of human arylamine N-acetyltransferase 1 by the hydroxylamine of p-aminobenzoic acid

Human N-acetyltransferase 1 (NAT1) is a widely distributed enzyme that catalyses the acetylation of arylamine and hydrazine drugs as well as several known carcinogens, and so its levels in the body may have toxicological importance with regard to drug toxicity and cancer risk. Recently, we showed that p-aminobenzoic acid (PABA) was able to down-regulate human NAT1 in cultured cells, but the exact mechanism by which PABA acts remains unclear. In the present study, we investigated the possibility that PABA-induced down-regulation involves its metabolism to N-OH-PABA, since N-OH-AAF functions as an irreversible inhibitor of hamster and rat NAT1. We show here that N-OH-PABA irreversibly inactivates human NAT1 both in cultured cells and cell cytosols in a time- and concentration-dependent manner. Maximal inactivation in cultured cells occurred within 4 hr of treatment, with a concentration of 30 μM reducing activity by 60 ± 7%. Dialysis studies showed that inactivation was irreversible, and cofactor (acetyl coenzyme A) but not substrate (PABA) completely protected against inactivation, indicating involvement of the cofactor-binding site. In agreement with these data, kinetic studies revealed a 4-fold increase in cofactor K_m, but no change in substrate K_m for N-OH-PABA-treated cytosols compared to control. We conclude that N-OH-PABA decreases NAT1 activity by a direct interaction with the enzyme and appears to be a result of covalent modification at the cofactor-binding site. This is in contrast to our findings for PABA, which appears to reduce NAT1 activity by down-regulating the enzyme, leading to a decrease in NAT1 protein content.     

Inhibitory effects of polyphenolic compounds on human arylamine N-acetyltransferase 1 and 2

Arylamine N-acetyltransferases (NAT) are important enzymes involved in the metabolic activation of aromatic and heterocyclic amines and inhibitors of NAT enzymes may be valuable as chemopreventive agents. Phytochemicals including cinnamic acid derivatives, various classes of flavonoids and coumarins were tested for the inhibitory activity on NAT1 and NAT2 from human liver and the human cholangiocarcinoma cell line: KMBC cells. Assays were performed using p-aminobenzoic acid and sulfamethazine as selective substrates for NAT1 and NAT2, respectively. NAT1 and NAT2 activities were present in liver cytosol. However, the KMBC cells showed only NAT1 activity. There was a marked difference in the ability of the test chemicals to inhibit NAT1 and NAT2. Caffeic acid, ferulic acid, gallic acid and EGCG inhibited NAT1 but not NAT2, whereas scopuletin and curcumin inhibited NAT2 but not NAT1. Quercetin, kaemferol and other flavonoids, except epicatechin and silymarin, inhibited both enzymes. The kinetics of inhibition of NAT1 by caffeic acid, EGCG and quercetin were of the non-competitive type, whereas that of NAT2 by quercetin, curcumin and kaemferol was also of the non-competitive type. The most potent inhibitor was quercetin, which has the inhibitory constants for NAT1 and NAT2 of 48.6?±?17.3 and 10.0?±?1.8?µM, respectively.     

circRNA作用于急性缺血性脑卒中的研究进展

环状RNA(circRNA)介导内源性竞争RNA(ceRNA)调控网络已经被证实在急性缺血性脑卒中（AIS）损伤后的病理和生理过程中发挥关键作用,且分子诊断工具广泛应用后发现circRNA有望成为AIS的生物标志物,对上述研究进行归纳,可拓宽对AIS发生发展机制的研究视野,为其诊断和治疗提供新思路。     

Lack of association between arylamine N-acetyltransferase 2 (NAT2) polymorphism and systemic sclerosis

Objectives It has been shown that exposure to some environmental toxins may induce scleroderma-like illness in predisposed individuals, but the etiopathogenesis of the idiopathic form of systemic sclerosis (SSc) remains obscure. The genetic background of this illness has been confirmed in multiple studies. We investigated whether patients with SSc differ from healthy subjects with regard to the enzymatic activity of polymorphic N-acetyltransferase 2 (NAT2).Methods The study was carried out in 39 patients with SSc; 15 fulfilled the criteria of diffuse SSc (dSSc) and 24 of limited SSc (lSSc); an ethnically matched control group consisted of 100 healthy volunteers. Acetylation phenotype was estimated using the isoniazid as a model drug. The most common mutations in the Caucasian population at positions 481T, 803G, 590A and 857A on the NAT2 gene were determined using the polymerase chain reaction–restriction fragment length polymorphism method with deoxyribonucleic acid (DNA) extracted from peripheral blood.Results In the group of patients with SSc, the frequency of fast acetylator genotypes was 38.5% (95% CI 23.4–55.4), while that for the genotypes coding slow acetylator status was 51.3% (95% CI 34.8–67.6).There was a strong correlation between NAT2 phenotype and NAT2 genotype with a concordance of 97%. We did not observe a preponderance of slow acetylators among patients with SSc and in two subsets of SSc. With the sample size analyzed in the present study, there is a 90% probability of detecting significant differences in distribution of slow, fast, and intermediate phenotypes between patients with SSc and controls, there is a difference of at least 30.3, 28.7 and 21.9% in the distribution of these phenotypes in the general population, respectively.Conclusion Acetylator status does not seem to be the significant factor in the development of SSc in patients with both subsets of this autoimmune disease, but further studies are required to confirm this conclusion.     

阿片受体的晶体结构和基因多态性研究进展

阿片受体是阿片类镇痛药的重要作用靶点,中度至重度疼痛的治疗大部分依赖于阿片类药物的使用。目前临床上常用的吗啡等阿片类镇痛药治疗指数窄并且具有较大的个体差异。而且常常伴随着一些严重的耐受性和成瘾性等副作用。深入认识阿片受体高分辨率结构特点,有助于一些基于结构研发的方法中开发治疗疼痛及成瘾药物。研究阿片受体的基因多态性有助于从分子生物学的角度解释个体间对阿片类药物反应存在的差异。     

Reconstruction of N-acetyltransferase 2 haplotypes using PHASE

The genotyping of N-acetyltransferase 2 (NAT2) by PCR/RFLP methods yields in a considerable percentage ambiguous results. To resolve this methodical problem a statistical approach was applied. PHASE v2.1.1, a statistical program for haplotype reconstruction was used to estimate haplotype pairs from NAT2 genotyping data, obtained by the analysis of seven single nucleotide polymorphisms relevant for Caucasians. In 1,011 out of 2,921 (35%) subjects the haplotype pairs were clearcut by the PCR/RFLP data only. For the majority of the data the applied method resulted in a multiplicity (2–4) of possible haplotype pairs. Haplotype reconstruction using PHASE v2.1.1 cleared this ambiguity in all cases but one, where an alternative haplotype pair was considered with a probability of 0.029. The estimation of the NAT2 haplotype is important because the assignment of the NAT2 alleles *12A, *12B, *12C or *13 to the rapid or slow NAT2 genotype has been discussed controversially. A clear assignment is indispensable in surveys of human bladder cancer caused by aromatic amine exposures. In conclusion, PHASE v2.1.1 software allowed an unambiguous haplotype reconstruction in 2,920 of 2,921 cases (>99.9%).     

CYP450酶特性及其应用研究进展

细胞色素P450（CYP450）是药物和其他内、外源物的主要代谢酶,本文综述了人体内参与药物代谢的几种主要代谢酶CYP3A4、CYP2D6、CYP2C9、CYP2C19、CYP2E1、CYP1A2和CYP2A6的分子生物学特征,中药对药物代谢酶的影响及药物代谢酶在临床药物治疗和新药研究过程中的应用。     

Arylamine N-acetyltransferase 2 genotype-dependent N-acetylation of isoniazid in cryopreserved human hepatocytes

Cryopreserved human hepatocytes were used to investigate the role of arylamine N-acetyltransferase 2 (NAT2; EC 2.3.1.5) polymorphism on the N-acetylation of isoniazid (INH). NAT2 genotype was determined by Taqman allelic discrimination assay and INH N-acetylation was measured by high performance liquid chromatography. INH N-acetylation rates in vitro exhibited a robust and highly significant (P<0.005) NAT2 phenotype-dependent metabolism. N-acetylation rates in situ were INH concentration- and time-dependent. Following incubation for 24 h with 12.5 or 100 µmol/L INH, acetyl-INH concentrations varied significantly (P = 0.0023 and P = 0.0002) across cryopreserved human hepatocytes samples from rapid, intermediate, and slow acetylators, respectively. The clear association between NAT2 genotype and phenotype supports use of NAT2 genotype to guide INH dosing strategies in the treatment and prevention of tuberculosis.