chitin synthase | 9030-18-6

• 物质功能分类: 生物化工 - 酶及辅酶类
• 分子结构分类: 糖基转移酶 - 转移酶 - 己糖基转移酶
• 英文名称: chitin synthase
• 英文别名: chitin-UDP N-acetylglucosaminyltransferase；chitin-uridine diphosphate acetylglucosaminyltransferase；chitin synthetase；trans-N-acetylglucosaminosylase；UDP-N-acetyl-D-glucosamine:chitin 4-beta-N-acetylglucosaminyl-transferase；UDP-N-acetyl-alpha-D-glucosamine:chitin 4-beta-N-acetylglucosaminyltransferase；SAM synthetase
• CAS: 9030-18-6

制备方法与用途

简介

几丁质合成酶（Chitin synthetase）与大多数执行复杂生理功能的酶一样，其实是一系列具有相似功能的酶共同完成一系列生化反应的结果。这种酶是生物合成几丁质的关键物质，而几丁质则是昆虫表皮和真菌细胞壁的重要组成部分。

存在形式

自然界中的几丁质主要有三种晶形：α-几丁质、β-几丁质和γ-几丁质。其中，α-几丁质是最主要的存在形式，研究最为深入；其次为β-几丁质，它具有较弱的分子内作用力及较高的生物活性和溶解性，这些特性使其极具应用前景；而γ-几丁质由于含量较少，相关研究也相对较少。

用途

几丁质合成酶（Chitin synthetase; CS）是一种膜结合的糖苷转化酶。在它的催化下，尿苷二磷酸酯-N-乙酰氨基葡萄糖（UDP-GlcNAc）可以被转化为几丁质。

反应信息

• 作为试剂：
  描述：

  L-蛋氨酸 、 [2,8-3H]ATP 在 乙二胺四乙酸 、 chitin synthase 、 potassium chloride 、 magnesium chloride 作用下， 生成 [2,8-(3)H-Adenosyl]-SAM
  参考文献：
  名称：

  RlmN and Cfr are Radical SAM Enzymes Involved in Methylation of Ribosomal RNA

  摘要：

  Posttranscriptional modifications of ribosomal RNA (rRNA) nucleotides are a common mechanism of modulating the ribosome's function and conferring bacterial resistance to ribosome-targeting antibiotics. One such modification is methylation of an adenosine nucleotide within the peptidyl transferase center of the ribosome mediated by the endogenous methyltransferase RImN and its evolutionarily related resistance enzyme Cfr. These methyltransferases catalyze methyl transfer to aromatic carbon atoms of the adenosine within a complex 23S rRNA substrate to form the 2,8-dimethylated product. RImN and Cfr are members of the Radical SAM superfamily and contain the characteristic cysteine-rich CX3CX2C motif. We demonstrate that both enzymes are capable of accommodating the requisite [4Fe-4S] cluster. S-Adenosylmethionine (SAM) is both the methyl donor and the source of a 5'-deoxyadenosyl radical, which activates the substrate for methylation. Detailed analyses of the rRNA requirements show that the enzymes can utilize protein-free 23S rRNA as a substrate, but not the fully assembled large ribosomal subunit, suggesting that the methylations take place during the assembly of the ribosome. The key recognition elements in the 23S rRNA are helices 90-92 and the adjacent single stranded RNA that encompasses A2503. To our knowledge, this study represents the first in vitro description of a methyl transfer catalyzed by a member of the Radical SAM superfamily, and it expands the catalytic repertoire of this diverse enzyme class. Furthermore, by providing information on both the timing of methylation and its substrate requirements, our findings have important implications for the functional consequences of Cfr-mediated modification of rRNA in the acquisition of antibiotic resistance.

  DOI：

  10.1021/ja910850y