真菌几丁质合酶的研究进展

真菌细胞壁几丁质的合成是一个复杂的过程, 其关键酶为几丁质合酶(CS)。近年来, 丝状真菌中的CS研究有了大的突破, 与酿酒酵母中只有3种CS不同, 丝状真菌中存在7种类别的CS。大部分临床和农业中重要的病原真菌都是丝状真菌, 文中对真菌中7种类别CS的结构和功能作了概述, 重点讨论了丝状真菌中重要的CS类别, 并介绍了CS作为抗真菌药物有效靶标的研究现状, 旨在为研究真菌CS及其抑制剂提供参考。     

几丁质合酶在人类致病真菌中的研究进展

抑制真菌细胞壁的合成常作为防治真菌感染的安全有效手段。几丁质是真菌细胞壁及隔膜的重要结构成分，几丁质合酶是催化几丁质合成的关键酶。真菌细胞中几丁质合酶家族的不同成员在调控几丁质的合成中存在着差异，因此产生不同的生物学效应。本文通过综述几丁质合酶在人体三大条件致病真菌白色念珠菌、烟曲霉、新生隐球菌中的研究进展，分析了几丁质合酶对真菌致病性影响的机制，总结了几丁质合酶调控真菌细胞增殖、形态转换、病原菌与宿主的相互作用和细胞壁损伤诱导的补偿效应，展望了抗真菌感染的新策略及关于真菌几丁质合酶的未来研究方向。     

真菌β-1,3-葡聚糖合酶——一种抗真菌药物的靶标

真菌β-1,3-葡聚糖合酶（β-1,3-glucan synthase,GS）是由催化亚基和调节亚基组成的酶复合体。在酿酒酵母中GS的催化亚基是由2个序列高度相似的基因FKS1和FKS2编码的,在其他酵母中也存在多个与酿酒酵母FKS相似的基因．而在大多数丝状真菌中只存在1个FKS基因。文中主要介绍酿酒酵母和其他重要真菌中FKS基因的研究进展．对FKS基因的结构、在细胞中的定位、以及调控机制作了概括,并讨论了以真菌β-1,3-葡聚糖合酶为靶标开发新的抗真菌药物的研究现状和发展前景。     

几丁质酶和β-1,3-葡聚糖酶基因研究进展

几丁质酶和β-1,3-葡聚糖酶是重要的水解酶,实践证明,转几丁质酶和β-1,3-葡聚糖酶基因植物能比较有效地抵抗真菌侵染。本综述了几丁质酶和β-1,3-葡聚糖酶结构分类、抗真菌机理．及其近年来在抗黄曲霉病研究中的应嗣研究,并对今后的研究及应用进行了预测。     

链霉菌S01菌株几丁质酶对植物病原真菌的拮抗作用

纯化后的链霉菌S01菌株几丁质酶用环柱法在PDA平板上对杨树腐烂病菌（Valsasordida）、葡萄孢菌（Botrytissp．AS3．266）、黄瓜黑腥病菌（Cladosporiumcucumerinrm）、辣椒疫病菌（Phytophlhoracopsici）、棉花黄萎病菌（Verliilliumalbo-atrum)、立枯丝核菌（Rhizoctonasolani）等植物病原真菌及产黄青霉（Penlcillumc     

真菌聚酮合酶基因分离方法的研究进展

真菌聚酮合酶在代谢中可催化合成多种具有重要生物学活性的次级代谢物,所以真菌聚酮合酶正逐渐成为药学、食品科学和农学等领域的研究热点。本文综述了近五年来建立的几种分离真菌聚酮合酶基因的方法。这些方法解决了真菌中聚酮合酶基因簇难以分离的问题,为改造和利用真菌聚酮合酶以及发掘真菌聚酮化合物资源提供了强有力的手段。     

西伯利亚蓼几丁质酶基因Class Ⅳ的克隆及生物信息学分析

根据西伯利亚蓼抑制消减文库（SSH）中获得的几丁质酶（CHI）基因的部分序列,采用RACE技术克隆了具完整编码区的cDNA序列,基因全长1017bp,开放阅读框编码270个氨基酸。序列分析表明,该基因的编码蛋白（PsCHI1）以前体形式存在,N端分别有22个氨基酸的信号肽和35个氨基酸的几丁质结合域（CBD）,C端199个氨基酸为催化区（CD）,连接CBD与CD的14个氨基酸为可变交联区,成熟蛋白为不含信号肽部分,呈碱性,带正电荷。PsCHI1与所选其它植物classⅣCHI前体序列具有高度的同源性（53％-69％）,而与classⅠ和classⅡCHI的氨基酸序列同源性较低,推测为植物classⅣCHI。根据日本水稻CHI晶体结构构建了PsCHI1三维分子模型,分析显示PsCHI1可以识别比classⅠ和classⅡCHI短的几丁质片段,并以其它植物CHI的已知结构域和功能为基础,确定PsCHI1具有能够水解真菌细胞壁的结构,推测其可能有抗病原微生物的功能。     

Chitin synthase homologs in three ectomycorrhizal truffles

Abstract Degenerate PCR primers were used to amplify a conserved gene portion coding chitin synthase from genomic DNA of six species of ectomycorrhizal truffles. DNA was extracted from both hypogeous fruitbodies and in vitro growing mycelium of Tuber borchii . A single fragment of about 600 bp was amplified for each species. The amplification products from Tuber magnatum, T. borchii and T. ferrugineum were cloned and sequenced, revealing a high degree of identity (91.5%) at the nucleotide level. On the basis of the deduced amino acid sequences these clones were assigned to class II chitin synthase. Southern blot experiments performed on genomic DNA showed that the amplification products derive from a single copy gene. Phylogenetic analysis of the nucleotide sequences of class II chitin synthase genes confirmed the current taxonomic position of the genus Tuber , and suggested a close relationship between T. magnatum and T. uncinatum .     

Putative Chitin Synthases from Branchiostoma floridae Show Extracellular Matrix-related Domains and Mosaic Structures

The transition from unicellular to multicellular life forms requires the development of a specialized structural component,the extracellular matrix(ECM).In Metazoans,there are two main supportive systems,which are based on chitin and collagen/hyaluronan,respectively.Chitin is the major constituent of fungal cell walls and arthropod exoskeleton.However,presence of chitin/chitooligosaccharides has been reported in lower chordates and during specific stages of vertebrate development.In this study,the occurrence of chitin synthases(CHSs) was investigated with a bioinformatics approach in the cephalochordate Branchiostoma floridae,in which the presence of chitin was initially reported in the skeletal rods of the pharyngeal gill basket.Twelve genes coding for proteins containing conserved amino acid residues of processive glycosyltransferases from GT2 family were found and 10 of them display mosaic structures with novel domains never reported previously in a chitin synthase.In particular,the presence of a discoidin(DS) and a sterile alpha motif(SAM) domain was found in nine identified proteins.Sequence analyses and homology modelling suggest that these domains might interact with the extracellular matrix and mediate protein-protein interaction.The multi-domain putative chitin synthases from B.floridae constitute an emblematic example of the explosion of domain innovation and shuffling which predate Metazoans.     

甲壳素脱乙酰酶的研究概况及展望

甲壳素脱乙酰酶(chitin deacetylase,CDA,E.C.3.5.1.41)是一种能催化脱去甲壳素分子中N-乙酰葡糖胺链上的乙酰基,使之变成壳聚糖的酶。而壳聚糖因其独特的性质被广泛应用于医药、食品、化工、化妆品等行业。对CDA的来源、分离纯化和酶学性质、结构和催化机制、基因的克隆表达及应用前景等方面的研究进行了综述,并分析出今后的主要研究方向应在CDA基因的克隆表达、CDA底物的改造及CDA的结构和催化机制等方面。     

真菌细胞溶壁酶的产酶培养和应用效果

从土样中分离的７１株木霉（Ｔｒｉｃｈｏｄｅｒｍａ ｓｐ．）筛选出一株分解几丁质和葡聚糖能力较强的菌株。该菌株在麸皮、稻草粉、硫酸铵和诱导物为主成份的固体培养基上,经过２５℃、８４ｈ的培养,产生较高的真菌细胞溶壁酶,能溶解酵母、毛霉、黑曲霉及食用菌等丝状菌丝体的细胞壁,形成原生质体,经选用酵母、毛霉等进行原生质体再生,效果较优。     

Regulation of Bacterial,Yeast and Plant Polysaccharide Synthases: Implications for the Regulation of Pollen-tube Callose Synthase

从细菌、酵母及植物多糖合成酶的调控看花粉管胼胝质酶的调控 李惠娟1* Antony BACIC1 Steve M.READ2     

Evolution and phylogenetic relationships of chitin synthases from yeasts and fungi

Chitin, the structural component that provides rigidity to the cell wall of fungi is the product of chitin synthases (Chs). These enzymes are not restricted to fungi, but are amply distributed in four of the five eukaryotic 'crown kingdoms'. Dendrograms obtained by multiple alignment of Chs revealed that fungal enzymes can be classified into two divisions that branch into at least five classes, independent of fungal divergence. In contrast, oomycetes and animals each possess a single family of Chs. These results suggest that Chs originated as a branch of beta-glycosyl-transferases, once the kingdom Plantae split from the evolutionary line of eukaryotes. The existence of a single class of Chs in animals and Stramenopiles, against the multiple families in fungi, reveals that Chs diversification occurred after fungi departed from these kingdoms, but before separation of fungal groups. Accordingly, each fungal taxon contains members with enzymes belonging to different divisions and classes. Multiple alignment revealed the conservation of specific motifs characteristic of class, division and kingdom, but the strict conservation of only three motifs QXXEY, EDRXL and QXRRW, and seven isolated amino acids in the core region of all Chs. Determination of different structural features in this region of Chs brought to light a noticeable conservation of secondary structure in the proteins.     

Chitin synthase genes in the arbuscular mycorrhizal fungus Glomus versiforme: full sequence of a gene encoding a class IV chitin synthase

Chitin synthase genes of the arbuscular mycorrhizal fungus Glomus versiforme were sought in an investigation of the molecular basis of fungal growth. Three DNA fragments (Gvchs1, Gvchs2 and Gvchs3) corresponding to the conserved regions of distinct chitin synthase (chs) genes were amplified by means of the polymerase chain reaction (PCR) with two sets of degenerate primers. Gvchs1 and Gvchs2 encode two class I chitin synthases, whereas Gvchs3 encodes a class IV chitin synthase. A genomic library was used to obtain the Gvchs3 complete gene (1194 amino acids), which shows a very close similarity to the class IV chitin synthase from Neurospora crassa.     

酶法破碎微生物细胞的研究进展

酶法细胞破碎技术不仅能提高胞内产物的提取效率、降低能耗,还能减少化学试剂的用量,更有利于环保。主要介绍酶法破碎细菌、真菌、微藻、原生菌类等微生物细胞的研究进展、工业化情况以及应用展望。