咖啡碱是茶叶、咖啡等饮料的主要品质成分及功能成分之一.在植物体内咖啡碱生物合成的核心途径为：黄嘌呤核苷→7-甲基黄嘌呤核苷→7-甲基黄嘌呤→可可碱→咖啡碱,其中包括3步由N-甲基转移酶催化的转甲基化反应和1步由核糖核苷水解酶催化的脱核苷反应.N-甲基转移酶是参与咖啡碱生物合成的关键酶类.介绍了植物中咖啡碱的基本情况及其生物合成途径,重点综述了咖啡碱合成N-甲基转移酶的酶学特性、NMTs的克隆、基因结构与功能的关系以及基因表达调控研究等方面国内外的研究进展,并对未来该领域的研究重点进行了探讨和展望.

Caffeine is one of the main quality and functional components in beverage such as tea, coffee, etc. At present, a xanthosine→7-methylxanthosine→7-methylxanthine→theobromine→caffeine pathway is supported as the major route to caffeine, and it is synthesized through three methylation reactions by N- methyltransferase and a nucleosidase reaction by nucleoside hydrolase. N- methyltransferases(NMTs) are important enzymes in caffeine synthesis process. In this paper, the profile of caffeine in plant and the pathway of caffeine synthesis were introduced, and the research progress on the enzymology properties, gene cloning and expression, the relationship of gene function and structure of NMTs involved in caffeine biosynthesis were mainly reviewed. Finally, the research emphasis in the field for the future was discussed and prospected.

DNA甲基转移酶1(DNMT1)作为DNA甲基转移酶(DNMT)家族的主要成员,对维持和调节肿瘤细胞全基因组和局部区域甲基化起着核心作用.DNMT1在妇科恶性肿瘤中高表达,引起基因DNA的甲基化异常,特别是抑癌基因的高甲基化,继而造成相关基因表达沉默,导致细胞的恶性生长.

DNMT1,the main member of the DNA methyltransferase (DNMT) family,plays a core role in maintaining and regulating tumor cell genome-wide and the local area methylation.DNMT1 is highly expressed in gynecological malignancies,which leads to abnormal DNA methylation of genes,especially high methylation of tumor suppressor genes,gene expression silencing,and malignant cell growth.

研究表明,肿瘤相关基因启动子区域的异常甲基化是引发肾癌的重要原因之一,并与肿瘤的分化、侵袭、转移、分期和预后等密切相关.检测相关抑癌基因甲基化有助于肾癌的早期诊断.甲基转移酶抑制剂可逆转肿瘤细胞的异常甲基化,并可增加其他化疗药物的疗效,在肾癌的治疗中起重要作用.

Researches show that the tumor related gene promoter methylation is an important reason of renal cancer and is closely associated with the differentiation,invasion,metastasis,staging and prognosis of tumor.Methylation detection of related tumor suppressor genes is helpful in early diagnosis of renal cancer.Methyltransferase inhibitors can reverse abnormal methylation of tumor cells,increase the curative effect of other chemotherapy drugs and play an important role in the treatment of renal cancer.

目的探讨临床分离的对氨基糖苷类耐药的肠杆菌科细菌产16S rRNA甲基化酶状况,分析其分子流行趋势及其耐药性形成和传播的机制。方法采用纸片扩散法筛选庆大霉素和/或阿米卡星耐药的肠杆菌科细菌;采用聚合酶链反应(PCR)扩增16S rRNA甲基化酶基因、氨基糖苷修饰酶基因、β-内酰胺酶基因;采用质粒接合试验验证16S rRNA甲基化酶的转移性;应用脉冲场凝胶电泳(PFGE)对16S rRNA甲基化酶基因阳性菌株进行分型。结果 201株对庆大霉素和/或阿米卡星耐药的肠杆菌科细菌中共检出38株16S rRNA甲基化酶阳性株(armA基因16株,rmtB基因22株)。其中30株可通过接合试验将耐药质粒转移至受体菌。blaCTX-M-14、blaTEM-1和blaSHV-12可连同armA或rmtB分别转移到11、20和7个接合子中。肺炎克雷伯菌、大肠埃希菌和阴沟肠杆菌分别被PFGE分为4、21和1个型别。结论本研究分离的肠杆菌科细菌16S rRNA甲基化酶以armA和rmtB为主要流行型别,且后者分离率较高。该甲基化酶可导致氨基糖苷类高水平耐药,而且酶编码基因位于质粒上,具有转移性,β-内酰胺酶基因和氟喹诺酮耐药决定因子可随之一同转移。

Objective To investigate the molecular epidemiological characterization and the drug resistance and prevalence mechanism of 16S rRNA methylase in aminoglycoside-resistant Enterobacteriaceae isolated clinically. Methods Gentamicin-and or amikacin-resistant Enterobacteriaceae were screened by disc diffusion method.16S rRNA methylase genes,aminoglycoside modification enzyme genes and beta-lactamase genes were amplified by polymerase chain reaction(PCR).The conjugal transfer of aminoglycoside-resistant determination was performed.Pulsed-field gel electrophoresis (PFGE)was carried out to analyze genotyping.Results A total of 16 armA gene and 22 rmtB gene 16S rRNA methylase positive isolates were identified.Plasmid conjugation experiments were successful with 30 armA- or rmtB-positive isolates.blaCTX-M-14,blaTEM-1 and blaSHV-12 co-transferred with armA or rmtB were transferred to 11,20 and 7 isolates.Klebsiella pneumoniae,Escherichia coli and Enterobacter cloacae were divided into 4,21 and 1

蛋白质精氨酸甲基转移酶(protein arginine methyltransferases,PRMTs)是催化S-腺苷-甲硫氨酸的甲基转移至蛋白质精氨酸胍基氮原子上的酶.精氨酸甲基化是一种重要的翻译后修饰方式,参与许多重要的细胞过程,包括DNA修复、RNA加工、转录调控和信号转导.近年来大量研究证实,PRMTs与呼吸系统疾病、心血管系统疾病、肿瘤、病毒感染、糖代谢及其相关疾病、自身免疫性疾病密切相关.明确PRMTs的异常表达对肺部疾病的影响对疾病的治疗有重要作用.

Protein arginine methyltransferases (PRMTs) are enzymes that catalyze the transfer of a methyl group from S-adenosyl-L-methionine into a guanidino nitrogen of protein arginine.Protein arginine methylation is a novel posttranslational modification that plays a pivotal role in a variety of intracellular events,such as DNA repair,RNA processing,transcriptional regulation,and signal transduction.Recently,many studies reveal that PRMTs are significantly associated with pulmonary diseases,cardiovascular diseases,cancer,infections,glucose metabolic diseases,and autoimmune diseases.The paper introduces the recent progresses in the influence of dysregulation of PRMTs on pulmonary diseases.