The CMP-legionaminic acid pathway in Campylobacter: Biosynthesis involving novel GDP-linked precursors
作者:Ian C Schoenhofen、Evgeny Vinogradov、Dennis M Whitfield、Jean-Robert Brisson、Susan M Logan
DOI:10.1093/glycob/cwp039
日期:2009.7
The sialic acid-like sugar 5,7-diacetamido-3,5,7,9-tetradeoxy-d-glycero-d-galacto-nonulosonic acid, or legion- aminic acid, is found as a virulence-associated cell-surface glycoconjugate in the Gram-negative bacteria Legionella pneumophila and Campylobacter coli. L. pneumophila serogroup 1 strains, causative agents of Legionnaire's disease, contain an α2,4-linked homopolymer of legionaminic acid within their lipopolysaccharide O-chains, whereas the gastrointestinal pathogen C. coli modifies its flagellin with this monosaccharide via O-linkage. In this work, we have purified and biochemically characterized 11 candidate biosynthetic enzymes from Campylobacter jejuni, thereby fully reconstituting the biosynthesis of legionaminic acid and its CMP-activated form, starting from fructose-6-P. This pathway involves unique GDP-linked intermediates, likely providing a cellular mechanism for differentiating between this and similar UDP-linked pathways, such as UDP-2,4-diacetamido-bacillosamine biosynthesis involved in N-linked protein glycosylation. Importantly, these findings provide a facile method for efficient large-scale synthesis of legionaminic acid, and since legionaminic acid and sialic acid share the same d-glycero-d-galacto absolute configuration, this sugar may now be evaluated for its potential as a sialic acid mimic.
唾液酸样糖5,7-二乙酰氨基-3,5,7,9-四脱氧-D-甘油-D-半乳糖-吡喃糖酸(或军团胺酸)是一种与毒性相关的细胞表面糖复合物,存在于革兰氏阴性细菌军团菌和弯曲杆菌中。军团菌血清1型菌株是军团病的病原体,其脂多糖O链中含有α2,4-连接的军团胺酸同聚物,而胃肠道病原体大肠杆菌则通过O连接将这种单糖修饰其鞭毛蛋白。在这项工作中,我们纯化了11种来自空肠弯曲杆菌的候选生物合成酶,并对其进行了生化表征,从而完全重建了从果糖-6-P开始的军团胺酸及其CMP活化形式的生物合成。该途径涉及独特的GDP连接中间体,可能为区分该途径与类似UDP连接途径(如参与N-连接蛋白糖基化的UDP-2,4-二乙酰氨基-杆菌糖胺生物合成)提供了细胞机制。重要的是,这些发现为有效大规模合成军团胺酸提供了一种简便的方法,由于军团胺酸和唾液酸具有相同的D-甘油-D-半乳糖绝对构象,因此现在可以评估这种糖作为唾液酸类似物的潜力。