Daffe M, McNeil M, Brennan P J
Department of Microbiology, Colorado State University, Fort Collins 80523.
Carbohydr Res. 1993 Nov 3;249(2):383-98. doi: 10.1016/0008-6215(93)84102-c.
The cell wall arabinogalactans of strains of Mycobacterium, Rhodococcus, and Nocardia were per-O-methylated, partially hydrolyzed with acid, and the resulting oligosaccharides were reduced and per-O-ethylated to yield per-O-alkylated oligoglycosyl alditol fragments. Analyses of these fragments by gas chromatography-mass spectrometry and of the intact solubilized polysaccharides by 1H and 13C NMR revealed the major structural features of the different arabinogalactans from representatives of the different genera. All of the mycobacterial products contained a homogalactan segment of alternating 5-linked alpha-galactofuranosyl (Galf) and 6-linked beta-Galf residues. The arabinan segment consisted of three major domains, linear 5-linked alpha-arabinofuranosyl (Araf) residues and branched (3-->5)-linked Araf units substituted with either 5-linked Araf or the disaccharide beta-Araf-(1-->2)-alpha-Araf at both branched positions. The recognition of these features in in vivo grown Mycobacterium leprae is an important development. The arabinan from strains of Nocardia contains a nonreducing-end motif composed of the linear trisaccharide, beta-Araf-(1-->2)-alpha-Araf-(1-->5)-Araf, attached to linear 5-linked alpha-Araf units. The galactan segment of the arabinogalactan of Nocardia sp. is composed of linear 5-linked beta-Galf units substituted in part at O-6 with terminal beta-glucosyl units. The two representative strains of Rhodococcus also differed in the composition of the galactan moiety; in addition to the 5-linked Galf, 2- and 3-linked beta-Galf units are present. The reducing end of the galactans, and therefore, apparently, of the entire arabinogalactans from all species from all genera, are apparently composed of the unit, rhamnosyl-(1-->3)-N-acetyl-glucosamine, which, in turn, is apparently attached to peptidoglycan via phosphodiester linkage.
对分枝杆菌属、红球菌属和诺卡氏菌属菌株的细胞壁阿拉伯半乳聚糖进行全 - O - 甲基化，用酸部分水解，所得寡糖经还原和全 - O - 乙基化，得到全 - O - 烷基化寡糖基糖醇片段。通过气相色谱 - 质谱对这些片段进行分析，并通过¹H和¹³C NMR对完整的可溶多糖进行分析，揭示了来自不同属代表的不同阿拉伯半乳聚糖的主要结构特征。所有分枝杆菌产物都含有一个由交替的5 - 连接的α - 呋喃半乳糖基（Galf）和6 - 连接的β - Galf残基组成的同型半乳聚糖片段。阿拉伯聚糖片段由三个主要结构域组成，线性的5 - 连接的α - 阿拉伯呋喃糖基（Araf）残基以及在两个分支位置被5 - 连接的Araf或二糖β - Araf - (1→2) - α - Araf取代的分支（3→5）连接的Araf单元。在体内生长的麻风分枝杆菌中识别出这些特征是一项重要进展。诺卡氏菌属菌株的阿拉伯聚糖含有一个由线性三糖β - Araf - (1→2) - α - Araf - (1→5) - Araf组成的非还原端基序，该基序连接到线性的5 - 连接的α - Araf单元上。诺卡氏菌属阿拉伯半乳聚糖的半乳聚糖片段由线性的5 - 连接的β - Galf单元组成，部分在O - 6位被末端β - 葡萄糖基单元取代。红球菌属的两个代表性菌株在半乳聚糖部分的组成上也有所不同；除了5 - 连接的Galf外，还存在2 - 和3 - 连接的β - Galf单元。所有属的所有物种的半乳聚糖的还原端，因此显然也是整个阿拉伯半乳聚糖的还原端，显然由鼠李糖基 - (1→3) - N - 乙酰葡糖胺单元组成，该单元又显然通过磷酸二酯键连接到肽聚糖上。
