Kasai K, Hirabayashi J
Faculty of Pharmaceutical Sciences, Teikyo University, Sagamiko, Kanagawa.
J Biochem. 1996 Jan;119(1):1-8. doi: 10.1093/oxfordjournals.jbchem.a021192.
Galectins, animal lectins exhibiting specificity for galactosides, are now known to be widely distributed from lower invertebrates, such as sponges and nematodes, to higher vertebrates. The origin of the family can be traced back to the Precambrian era. They are classified into proto-, chimera-, and tandem-repeat types on the basis of protein architecture. The molecular functions of these types should be different because they can cross-link pairs of biomolecules of different combinations. Their biological significance, however, is not yet fully understood because they are involved in too many phenomena, such as differentiation, morphogenesis, metastasis, etc., and too many problems remain unsolved, such as those regarding their controversial cellular localization, mechanism of externalization, etc. Nevertheless, such difficulties seem to indicate their importance as household equipment and their common roles throughout the animal kingdom. They are likely to be responsible for recognizing the N-acetyllactosamine (LacNAc) structure, which is included in various glycoconjugates and considered to be an important glycocode, and then carry out appropriate tasks under given circumstances. Recently, crystallographic studies revealed that galectins and legume lectins such as concanavalin A have a common topology in spite of the absence of sequence homology. This suggests a possible relationship between animal and plant lectins, and the existence of a lectin super family. Studies on the galectin family are becoming increasingly important for glycobiology.
半乳糖凝集素是一类对半乳糖苷具有特异性的动物凝集素，现已发现其广泛分布于从海绵和线虫等低等无脊椎动物到高等脊椎动物的各类生物中。该家族的起源可追溯到前寒武纪时代。根据蛋白质结构，它们可分为原聚体型、嵌合型和串联重复型。由于这些类型能够交联不同组合的生物分子对，所以它们的分子功能应该有所不同。然而，它们的生物学意义尚未完全明晰，因为它们涉及众多现象，如分化、形态发生、转移等，并且还有许多问题尚未解决，比如它们备受争议的细胞定位、外化机制等。尽管如此，这些困难似乎表明了它们作为“家用设备”的重要性以及在整个动物界的共同作用。它们可能负责识别包含在各种糖缀合物中且被视为重要糖代码的N - 乙酰乳糖胺（LacNAc）结构，然后在特定情况下执行相应任务。最近，晶体学研究表明，尽管半乳糖凝集素与诸如伴刀豆球蛋白A等豆科凝集素不存在序列同源性，但它们具有共同的拓扑结构。这表明动物凝集素与植物凝集素之间可能存在关联，以及存在一个凝集素超家族。对半乳糖凝集素家族的研究在糖生物学中变得越来越重要。
