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首页> 外文期刊>The FEBS journal >Towards understanding the functional role of the glycosyltransferases involved in the biosynthesis of Moraxella catarrhalis lipooligosaccharide
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Towards understanding the functional role of the glycosyltransferases involved in the biosynthesis of Moraxella catarrhalis lipooligosaccharide

机译：理解糖基转移酶在卡他莫拉氏菌脂联低聚糖生物合成中的功能作用

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摘要

The glycosyltransferase enzymes (Lgts) responsible for the biosynthesis of the lipooligosaccharide-derived oligosaccharide structures from Moraxella catarrhalis have been investigated. This upper respiratory tract pathogen is responsible for a spectrum of illnesses, including otitis media (middle ear infection) in children, and contributes to exacerbations of chronic obstructive pulmonary disease in elderly patients. To investigate the function of the glycosyltransferase enzymes involved in the biosynthesis of lipooligosaccharide of M. catarrhalis and to gain some insight into the mechanism of serotype specificity for this microorganism, mutant strains of M. catarrhalis were produced. Examination by NMR and MS of the oligosaccharide structures produced by double-mutant strains (2951lgt1/4 Delta and 2951lgt5/4 Delta) and a single-mutant strain (2951lgt2 Delta) of the bacterium has allowed us to propose a model for the serotype-specific expression of lipooligosaccharide in M. catarrhalis. According to this model, the presence/absence of Lgt4 and the Lgt2 allele determines the lipooligosaccharide structure produced by a strain. Furthermore, it is concluded that Lgt4 functions as an N-acetylglucosylamine transferase responsible for the addition of an alpha-D-GlcNAc (1 -> 2) glycosidic linkage to the (1 -> 4) branch, and also that there is competition between the glycosyltransferases Lgt1 and Lgt4. That is, in the presence of an active Lgt4, GlcNAc is preferentially added to the (1 -> 4) chain of the growing oligosaccharide, instead of Glc. In serotype B strains, which lack Lgt4, Lgt1 adds a Glc at this position. This implies that active Lgt4 has a much higher affinity/specificity for the beta-(1 -> 4)-linked Glc on the (1 -> 4) branch than does Lgt1.
机译：已经研究了负责从卡他莫拉氏菌中脂寡糖衍生的寡糖结构生物合成的糖基转移酶（Lgts）。这种上呼吸道病原体引起多种疾病，包括儿童中耳炎（中耳感染），并导致老年患者慢性阻塞性肺疾病的加重。为了研究参与卡他莫拉氏菌脂寡糖生物合成的糖基转移酶的功能并获得对该微生物的血清型特异性机制的一些见识，产生了卡他拉莫氏菌的突变菌株。通过NMR和MS对细菌的双突变株（2951lgt1 / 4 Delta和2951lgt5 / 4 Delta）和单突变株（2951lgt2 Delta）产生的寡糖结构的研究，使我们能够提出血清型的模型脂寡糖在粘膜炎莫拉氏菌中的特异性表达根据该模型，Lgt4和Lgt2等位基因的存在/不存在决定了菌株产生的脂寡糖结构。此外，得出的结论是，Lgt4充当N-乙酰基葡糖胺转移酶，负责将α-D-GlcNAc（1-> 2）糖苷键添加到（1-> 4）分支，并且之间存在竞争糖基转移酶Lgt1和Lgt4。即，在活性Lgt4的存在下，代替Glc，将GlcNAc优先添加至生长的寡糖的（1→4）链。在缺少Lgt4的B型血清型菌株中，Lgt1在此位置添加了一个Glc。这意味着活性Lgt4对（1-> 4）分支上与β-（1-> 4）连接的Glc的亲和力/特异性比Lgt1高得多。

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