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首页> 外文期刊>Journal of bacteriology >Unraveling the Function of Glycosyltransferases in Streptococcus thermophilus Sfi6
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Unraveling the Function of Glycosyltransferases in Streptococcus thermophilus Sfi6

机译：揭示嗜热链球菌Sfi6中糖基转移酶的功能

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Streptococcus thermophilus Sfi6 produces a texturizing exopolysaccharide (EPS) consisting of a →3)[α-d-Galp-(1→6)]-β-d-Glcp-(1→3)-α-d-GalpNAc-(1→3)-β-d-Galp-(1→?repeating unit. We previously identified and analyzed a 14.5-kb gene cluster fromS. thermophilus Sfi6 consisting of 13 genes responsible for its EPS production. Within this gene cluster, we found a central region of genes (epsE, epsF, epsG, andepsI) that showed similarity to glycosyltransferases. In this study, we investigated the sugar specificity of these enzymes. EpsE catalyzes the first step in the biosynthesis of the EPS repeating unit. It exhibits phosphogalactosyltransferase activity and transfers galactose onto the lipophilic carrier. The second step is fulfilled by EpsG, which transfers an α-N-acetylgalactosamine onto the first β-galactoside. The activity of EpsF was determined by characterizing the EPS produced by an S. thermophilus epsFdeletion mutant. This EPS consisted of the monosaccharides Gal, Glc, and GalNAc in an approximately equimolar ratio, thus suggesting thatepsF codes for the branching galactosyltransferase.epsI probably codes for the β-1,3-glucosyltransferase, since it is the only glycosyltransferase to which no gene has been assigned and it exhibits similarity to other β-glycosyltransferases. EpsE shows the conserved features of phosphoglycosyltransferases, whereas EpsF and EpsG exhibit the primary structure of α-glycosyltransferases, belonging to glycosyltransferase family 4, whose members are conserved in all major phylogenetic lineages, including the Archaea and Eukaryota.
机译：嗜热链球菌 Sfi6产生由→3）[α-d-Gal p -（1→6）]-β-d-Glc组成的变形胞外多糖（EPS） p -（1→3）-α-d-Gal p NAc-（1→3）-β-d-Gal p - （1→？重复单元。我们先前从嗜热链球菌Sfi6中鉴定并分析了一个14.5kb基因簇，该簇由负责其EPS产生的13个基因组成。与糖基转移酶相似的基因（ epsE ， epsF ， epsG 和 epsI ）。我们研究了这些酶的糖特异性，EpsE催化了EPS重复单元生物合成的第一步，它具有磷酸半乳糖基转移酶活性并将半乳糖转移到亲脂性载体上，第二步由EpsG完成，后者转移了α- N -乙酰半乳糖胺到第一个β-半乳糖苷上，通过表征 S。嗜热菌epsF 缺失突变体。该EPS由大约等摩尔比的单糖Gal，Glc和GalNAc组成，因此提示 epsF 编码分支半乳糖基转移酶。 epsI 可能编码β-1。 ，3-葡萄糖基转移酶，因为它是唯一未分配基因的糖基转移酶，并且与其他β-糖基转移酶表现出相似性。 EpsE显示磷酸糖基转移酶的保守特征，而EpsF和EpsG显示α-糖基转移酶的主要结构，属于糖基转移酶家族4，其成员在所有主要系统发育谱系中都保守，包括 Archaea 和真核生物。

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