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首页> 外文期刊>Infection and immunity >Presence of Active Aliphatic Amidases in Helicobacter Species Able To Colonize the Stomach
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Presence of Active Aliphatic Amidases in Helicobacter Species Able To Colonize the Stomach

机译：能够在胃中定殖的幽门螺杆菌中活性脂肪酰胺酶的存在

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Ammonia production is of great importance for the gastric pathogen Helicobacter pylori as a nitrogen source, as a compound protecting against gastric acidity, and as a cytotoxic molecule. In addition to urease, H. pylori possesses two aliphatic amidases responsible for ammonia production: AmiE, a classical amidase, and AmiF, a new type of formamidase. Both enzymes are part of a regulatory network consisting of nitrogen metabolism enzymes, including urease and arginase. We examined the role of the H. pylori amidases in vivo by testing the gastric colonization of mice with H. pylori SS1 strains carrying mutations in amiE and/or amiF and in coinfection experiments with wild-type and double mutant strains. A new cassette conferring resistance to gentamicin was used in addition to the kanamycin cassette to construct the double mutation in strain SS1. Our data indicate that the amidases are not essential for colonization of mice. The search for amiE and amiF genes in 53 H. pylori strains from different geographic origins indicated the presence of both genes in all these genomes. We tested for the presence of the amiE and amiF genes and for amidase and formamidase activities in eleven Helicobacter species. Among the gastric species, H. acinonychis possessed both amiE and amiF, H. felis carried only amiF, and H. mustelae was devoid of amidases. H. muridarum, which can colonize both mouse intestine and stomach, was the only enterohepatic species to contain amiE. Phylogenetic trees based upon the sequences of H. pylori amiE and amiF genes and their respective homologs from other organisms as well as the amidase gene distribution among Helicobacter species are strongly suggestive of amidase acquisition by horizontal gene transfer. Since amidases are found only in Helicobacter species able to colonize the stomach, their acquisition might be related to selective pressure in this particular gastric environment.
机译：氨的产生对于胃病原体幽门螺杆菌（Helicobacter pylori）作为氮源，作为防止胃酸的化合物和细胞毒性分子非常重要。除脲酶外， H。幽门螺旋菌具有两种氨产生的脂族酰胺酶：经典的酰胺酶AmiE和新型的甲酰胺酶AmiF。两种酶都是由氮代谢酶（包括脲酶和精氨酸酶）组成的调节网络的一部分。我们研究了 H的作用。通过用 H检测小鼠的胃部定植，在体内产生幽门螺杆菌酰胺酶。 pylori SS1菌株携带 amiE 和/或 amiF 以及在野生型和双重突变菌株的共染实验中携带突变。除了卡那霉素盒外，还使用了赋予庆大霉素抗性的新盒来构建菌株SS1的双重突变。我们的数据表明酰胺酶对于小鼠定植不是必需的。在53个 H中搜索 amiE 和 amiF 基因。来自不同地理来源的幽门螺杆菌菌株表明在所有这些基因组中都存在这两个基因。我们测试了11种 Helicobacter 物种中 amiE 和 amiF 基因的存在以及酰胺酶和甲酰胺酶的活性。在胃中， H。刺虾同时拥有 amiE 和 amiF ， H。 felis 仅携带 amiF 和 H。鼬不含酰胺酶。 H。 muridarum 可以在小鼠的肠道和胃部定植，是唯一含有 amiE 的肠肝菌种。基于 H序列的系统发生树。幽门螺杆菌amiE 和 amiF 基因以及它们各自来自其他生物的同源物，以及 Helicobacter 物种中酰胺酶的基因分布强烈暗示了通过水平基因转移获得酰胺酶。由于酰胺酶仅在能够定殖于胃的 Helicobacter 物种中发现，因此其获取可能与在这种特定胃环境中的选择性压力有关。

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