Kenyon Johanna J, Speciale Immacolata, Hall Ruth M, De Castro Cristina
School of Molecular Bioscience, University of Sydney, Australia; Institute of Health and Biomedical Innovation, Queensland University of Technology, Australia.
Department of Chemical Sciences, University of Napoli, Italy.
Carbohydr Res. 2016 Nov 3;434:12-17. doi: 10.1016/j.carres.2016.07.016. Epub 2016 Jul 15.
The structure of the K4 capsular polysaccharide (CPS) from a multiply antibiotic resistant Acinetobacter baumannii isolate D78 was elucidated by chemical and spectroscopical analysis. The K4 repeating unit is composed entirely by aminosugars and the trisaccharide repeating unit of the backbone polysaccharide is branched with a terminal N-acetyl-galactosamine capped with pyruvate as cyclic acetal. Each residue is in the pyranose form, α configured at the anomeric center, and has the D absolute configuration. The genes responsible for the synthesis of the K4 repeat unit and its polymerization and export are found in the capsule locus KL4 present in D78. The pyruvate acetal addition to galactosamine is formed by Ptr1, a novel pyruvate transferase, encoded at this locus.
通过化学和光谱分析阐明了多重耐药鲍曼不动杆菌分离株D78的K4荚膜多糖（CPS）的结构。K4重复单元完全由氨基糖组成，主链多糖的三糖重复单元带有一个末端N-乙酰半乳糖胺，其被丙酮酸封端形成环状缩醛。每个残基均为吡喃糖形式，在异头中心为α构型，并且具有D绝对构型。负责K4重复单元合成及其聚合和输出的基因位于D78中存在的荚膜基因座KL4中。半乳糖胺上的丙酮酸缩醛加成是由该基因座编码的新型丙酮酸转移酶Ptr1形成的。
