Department of Immunoregulation, Research Institute for Microbial Diseases, Osaka University, Osaka, Japan.
Biochem Biophys Res Commun. 2011 Nov 18;415(2):421-5. doi: 10.1016/j.bbrc.2011.10.085. Epub 2011 Oct 21.
The procyclic stage of Trypanosoma brucei is covered by glycosylphosphatidylinositol (GPI)-anchored surface proteins called procyclins. The procyclin GPI anchor contains a side chain of N-acetyllactosamine repeats terminated by sialic acids. Sialic acid modification is mediated by trans-sialidases expressed on the parasite's cell surface. Previous studies suggested the presence of more than one active trans-sialidases, but only one has so far been reported. Here we cloned and examined enzyme activities of four additional trans-sialidase homologs, and show that one of them, Tb927.8.7350, encodes another active trans-sialidase, designated as TbSA C2. In an in vitro assay, TbSA C2 utilized α2-3 sialyllactose as a donor, and produced an α2-3-sialylated product, suggesting that it is an α2-3 trans-sialidase. We suggest that TbSA C2 plays a role in the sialic acid modification of the trypanosome cell surface.
布氏锥虫的循环型阶段被糖基磷脂酰肌醇（GPI）锚定的表面蛋白覆盖，这些蛋白称为前锥虫蛋白。前锥虫 GPI 锚含有 N-乙酰乳糖胺重复侧链，末端为唾液酸。唾液酸修饰由寄生虫细胞表面表达的转涎酸酶介导。先前的研究表明存在不止一种活性转涎酸酶，但迄今为止只报道了一种。在这里，我们克隆并检查了另外四个转涎酸酶同源物的酶活性，并表明其中一个，Tb927.8.7350，编码另一种活性转涎酸酶，命名为 TbSA C2。在体外测定中，TbSA C2 以 α2-3 唾液乳糖作为供体，并产生 α2-3-唾液酸化产物，表明它是一种 α2-3 转涎酸酶。我们认为 TbSA C2 在锥虫细胞表面的唾液酸修饰中发挥作用。
