Department of Biochemistry, School of Pharmaceutical Sciences, University of Shizuoka, 52-1 Yada, Suruga-ku, Shizuoka 422-8526, Japan.
FEBS Open Bio. 2013 May 29;3:231-6. doi: 10.1016/j.fob.2013.05.002. Print 2013.
In a comparison of sialidase activities toward N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc), we found that Salmonella typhimurium LT2 sialidase (STSA) hardly cleaved 4-methylumbelliferyl Neu5Gc (4MU-Neu5Gc). The k cat/K m value of STSA for 4MU-Neu5Gc was found to be 110 times lower than that for 4-methylumbelliferyl Neu5Ac (4MU-Neu5Ac). Additionally, STSA had remarkably weak ability to cleave α2-3-linked-Neu5Gc contained in gangliosides and equine erythrocytes. In silico analysis based on first-principle calculations with transition-state analogues suggested that the binding affinity of Neu5Gc2en is 14.3 kcal/mol more unstable than that of Neu5Ac2en. The results indicated that STSA preferentially cleaves Neu5Ac residues rather than Neu5Gc residues, which is important for anyone using this enzyme to cleave α2-3-linked sialic acids.
在唾液酸酶对 N-乙酰神经氨酸（Neu5Ac）和 N-羟乙酰神经氨酸（Neu5Gc）的活性比较中，我们发现鼠伤寒沙门氏菌 LT2 唾液酸酶（STSA）几乎不能切割 4-甲基伞形酮 N-乙酰神经氨酸（4MU-Neu5Ac）。STSA 对 4-甲基伞形酮 N-羟乙酰神经氨酸（4MU-Neu5Gc）的 k cat/K m 值比 4-甲基伞形酮 N-乙酰神经氨酸（4MU-Neu5Ac）低 110 倍。此外，STSA 对神经节苷脂和马红细胞中含有的 α2-3 连接的 Neu5Gc 几乎没有切割能力。基于过渡态类似物的第一性原理计算的计算分析表明， Neu5Gc2en 的结合亲和力比 Neu5Ac2en 不稳定 14.3 kcal/mol。结果表明，STSA 优先切割 Neu5Ac 残基而不是 Neu5Gc 残基，这对于使用该酶切割 α2-3 连接的唾液酸的任何人都很重要。
