Engstler M, Reuter G, Schauer R
Biochemisches Institut, Christian-Albrechts-Universität, Kiel, Germany.
Mol Biochem Parasitol. 1993 Sep;61(1):1-13. doi: 10.1016/0166-6851(93)90153-o.
A developmentally regulated trans-sialidase activity is present on the surface of procyclic Trypanosoma brucei. Bloodstream stages display no trans-sialidase activity. T. brucei trans-sialidase is capable of transferring sialic acids from a variety of glycoconjugates into new glycosidic linkages without requirement for CMP-Neu5Ac. The enzyme is linked to the plasma-membrane via a GPI-PLC-resistant GPI-anchor. The comparison of enzymic and structural features of sialidase and trans-sialidase suggests that the two activities may be catalyzed by the same protein, since highly enriched sialidase fractions display trans-sialidase activity. 2-Deoxy-2,3-didehydro-N-acetylneuraminic acid is only a poor inhibitor for the two enzymic activities. Sialic acids are transferred to alpha (2-3)-positions of terminal beta-galactose residues of oligosaccharides and glycoconjugates at various rates. Neu5Ac-alpha(2-3)-lactose is the best trans-sialylation donor tested. Lewis is a poor sialic acid acceptor. T. brucei trans-sialidase utilizes serum glycoconjugates, human and bovine erythrocytes as sialic acid donors, and resialylates sialidase-treated erythrocytes. The enzyme transfers sialic acids from the GPI-anchor of procyclic acidic repetitive protein (PARP) onto lactose and vice versa. Also structures within a variant surface glycoprotein (sVSG MITat. 1.7.) can be trans-sialylated.
在布氏锥虫前循环期虫体表面存在一种受发育调控的转唾液酸酶活性。血流期虫体则无转唾液酸酶活性。布氏锥虫转唾液酸酶能够将多种糖缀合物中的唾液酸转移至新的糖苷键中，且无需CMP - Neu5Ac。该酶通过一种对GPI - PLC有抗性的GPI锚定连接于质膜。唾液酸酶和转唾液酸酶的酶学及结构特征比较表明，这两种活性可能由同一蛋白质催化，因为高度纯化的唾液酸酶组分显示出转唾液酸酶活性。2 - 脱氧 - 2,3 - 二脱氢 - N - 乙酰神经氨酸对这两种酶活性的抑制作用较弱。唾液酸以不同速率转移至寡糖和糖缀合物末端β - 半乳糖残基的α(2 - 3)位。Neu5Ac - α(2 - 3) - 乳糖是所测试的最佳转唾液酸化供体。Lewis是较差的唾液酸受体。布氏锥虫转唾液酸酶利用血清糖缀合物、人和牛红细胞作为唾液酸供体，并对经唾液酸酶处理的红细胞进行再唾液酸化。该酶将前循环期酸性重复蛋白（PARP）的GPI锚上的唾液酸转移至乳糖，反之亦然。可变表面糖蛋白（sVSG MITat. 1.7.）中的结构也可被转唾液酸化。
