Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390-9185, USA.
ACS Chem Biol. 2012 Sep 21;7(9):1509-14. doi: 10.1021/cb300241v. Epub 2012 Jun 26.
Sialidases hydrolytically remove sialic acids from sialylated glycoproteins and glycolipids. Sialidases are widely distributed in nature and sialidase-mediated desialylation is implicated in normal and pathological processes. However, mechanisms by which sialidases exert their biological effects remain obscure, in part because sialidase substrate preferences are poorly defined. Here we report the design and implementation of a sialidase substrate specificity assay based on chemoselective labeling of sialosides. We show that this assay identifies components of glycosylated substrates that contribute to sialidase specificity. We demonstrate that specificity of sialidases can depend on structure of the underlying glycan, a characteristic difficult to discern using typical sialidase assays. Moreover, we discovered that Streptococcus pneumoniae sialidase NanC strongly prefers sialosides containing the Neu5Ac form of sialic acid versus those that contain Neu5Gc. We propose using this approach to evaluate sialidase preferences for diverse potential substrates.
唾液酸酶通过水解作用从唾液酸化糖蛋白和糖脂中去除唾液酸。唾液酸酶广泛存在于自然界中，唾液酸酶介导的去唾液酸化作用与正常和病理过程有关。然而，唾液酸酶发挥其生物学效应的机制仍不清楚，部分原因是唾液酸酶的底物偏好定义不明确。本文报告了一种基于唾液酸选择性化学标记的唾液酸酶底物特异性测定方法的设计和实施。结果表明，该测定方法可识别糖基化底物中有助于唾液酸酶特异性的成分。结果表明，唾液酸酶的特异性可能取决于潜在聚糖的结构，而使用典型的唾液酸酶测定方法很难辨别这一特征。此外，研究人员发现肺炎链球菌唾液酸酶 NanC 强烈偏爱含有 Neu5Ac 形式唾液酸的唾液酸苷，而不是含有 Neu5Gc 的唾液酸苷。研究人员提出使用这种方法来评估唾液酸酶对各种潜在底物的偏好。
