Lee R E, Brennan P J, Besra G S
Department of Microbiology, Colorado State University, Fort Collins 80523-1677, USA.
Glycobiology. 1997 Dec;7(8):1121-8. doi: 10.1093/glycob/7.8.1121.
Information on the biosynthesis of the D-arabinans of the cell wall of Mycobacterium tuberculosis is rapidly emerging, with the promise of new targets for drug development against tuberculosis. Accordingly, arabinosyl transferase assays were developed utilizing synthesized [1-14C]-beta-D-arabinofuranosyl-1-monophosphoryldecaprenol as donor and a variety of O- and S-alkyl arabinosides as acceptors. These were: alpha-D-Araf-(1-->5)-alpha-D-Araf-O- and -S-alkyl diarabinosides and alpha-D-Araf-(1-->5)-alpha-D-Araf-(1-->5)-alpha-D-Araf -O- and -S-alkyl triarabinosides. Whereas the O- and S-alkyl monosaccharide acceptors were inactive, the O- and S-alkyl disaccharide and the O- and S-alkyl trisaccharide acceptors (<C12) possessed considerable acceptor activity, and the trisaccharide acceptors were more potent than the corresponding disaccharides. The O-alkyl disaccharide acceptors with a C8 alkyl chain were more active than those containing the C6 or C10 analogs. Chemical analysis of the enzymatically synthesized products of the reactions demonstrated that beta-D-arabinofuranosyl-1-monophosphoryldecaprenol was an effective donor for two of the three potential arabinosyl transferases: beta-D-arabinofuranosyl-1-monophosphoryldecaprenol: arabinan alpha(1-->5) arabinosyl transferase and beta-D-arabinofuranosyl-1-monophosphoryldecaprenol: arabinan beta(1-->2) arabinosyl transferase. The beta(1-->2) arabinosyl transferase activity was more in evidence in the presence of the O-alkyl disaccharide acceptor, whereas both transferases were about equivalent in the presence of the S-alkyl trisaccharide acceptor. The tuberculosis drug, ethambutol, a known mycobacterial arabinosyl transferase inhibitor, was inactive within these arabinosyl transferase/acceptor based assay systems, supporting other evidence that a third activity, responsible for the formation of alpha1-->3 linkage, is the drug target.
关于结核分枝杆菌细胞壁D - 阿拉伯聚糖生物合成的信息正在迅速涌现，有望为抗结核药物开发提供新的靶点。因此，利用合成的[1 - ¹⁴C] - β - D - 阿拉伯呋喃糖基 - 1 - 单磷酸十聚戊烯醇作为供体，以及多种O - 和S - 烷基阿拉伯糖苷作为受体，开发了阿拉伯糖基转移酶测定法。这些受体包括：α - D - Araf - (1→5) - α - D - Araf - O - 和 - S - 烷基二阿拉伯糖苷以及α - D - Araf - (1→5) - α - D - Araf - (1→5) - α - D - Araf - O - 和 - S - 烷基三阿拉伯糖苷。虽然O - 和S - 烷基单糖受体无活性，但O - 和S - 烷基二糖以及O - 和S - 烷基三糖受体（<C12）具有相当的受体活性，且三糖受体比相应的二糖更有效。具有C8烷基链的O - 烷基二糖受体比含有C6或C10类似物的受体更具活性。对反应的酶促合成产物进行化学分析表明，β - D - 阿拉伯呋喃糖基 - 1 - 单磷酸十聚戊烯醇是三种潜在阿拉伯糖基转移酶中两种的有效供体：β - D - 阿拉伯呋喃糖基 - 1 - 单磷酸十聚戊烯醇：阿拉伯聚糖α(1→5)阿拉伯糖基转移酶和β - D - 阿拉伯呋喃糖基 - 1 - 单磷酸十聚戊烯醇：阿拉伯聚糖β(1→2)阿拉伯糖基转移酶。在O - 烷基二糖受体存在下，β(1→2)阿拉伯糖基转移酶活性更明显，而在S - 烷基三糖受体存在下，两种转移酶活性大致相当。结核药物乙胺丁醇是一种已知的分枝杆菌阿拉伯糖基转移酶抑制剂，在这些基于阿拉伯糖基转移酶/受体的测定系统中无活性，这支持了其他证据，即负责形成α1→3连接的第三种活性是药物靶点。
