Varki A
Cancer Center, University of California, San Diego, La Jolla 92093-0687, USA.
FASEB J. 1997 Mar;11(4):248-55. doi: 10.1096/fasebj.11.4.9068613.
The sialic acids are acidic monosaccharides typically found at the outermost ends of the sugar chains of animal glycoconjugates. They potentially can inhibit intermolecular and intercellular interactions by virtue of their negative charge. However, they can also act as critical components of ligands recognized by a variety of proteins of animal, plant, and microbial origin (sialic acid binding lectins). Recognition can be affected by specific structural variations and modifications of sialic acids, their linkage to the underlying sugar chain, the structure of these chains, and the nature of the glycoconjugate to which they are attached. Presented here is a summary of the various proteins that can recognize and bind to this family of monosaccharides, comparing and contrasting the structural requirements and mechanisms involved in binding. Particular attention is focused on the recently evolving information about sialic acid recognition by certain C-type lectins (the selectins), I-type lectins (e.g., CD22 and sialoadhesin), and a complement regulatory protein (the H protein). The last two instances are examples of the importance of the side chain of sialic acids and the effects of natural substitutions (e.g., 9-O-acetylation) of this part of the molecule.
唾液酸是酸性单糖，通常存在于动物糖缀合物糖链的最末端。它们可能因其负电荷而抑制分子间和细胞间的相互作用。然而，它们也可以作为动物、植物和微生物来源的多种蛋白质（唾液酸结合凝集素）识别的配体的关键组成部分。识别可能会受到唾液酸的特定结构变异和修饰、它们与下层糖链的连接、这些糖链的结构以及它们所连接的糖缀合物的性质的影响。本文总结了能够识别并结合这一单糖家族的各种蛋白质，比较并对比了结合过程中涉及的结构要求和机制。特别关注了有关某些C型凝集素（选择素）、I型凝集素（如CD22和唾液酸粘附素）以及一种补体调节蛋白（H蛋白）对唾液酸识别的最新进展信息。后两个例子说明了唾液酸侧链的重要性以及该分子这一部分的天然取代（如9-O-乙酰化）的影响。
