Evolution and function of galectins in : Comparison with mammals and new perspectives.

Galectins are metal-independent sugar-binding proteins that recognize galactose (the β-galactoside structure) and regulate the cross-linking of sugar chains between cells and the extracellular matrix. Their specificity for galactose is attributed to their highly conserved carbohydrate recognition domain. Galectins participate in biological processes across species, including development, differentiation, morphogenesis, tumor progression, metastasis, immunity, and apoptosis. However, the relationship between the binding of galectin to sugar chains (glycans) and their biological functions remains unclear. Thus, a comprehensive functional analysis of galectins is required to better characterize their evolutionarily conserved and unique functions. We have previously identified and characterized 12 galectins (xgalectins), the only non-mammalian vertebrate species in which galectins have been comprehensively characterized to date. In this review, we present the latest findings on the types and functions of xgalectins and discuss prospects for elucidating their diverse functions from an evolutionary perspective through comparisons with mammalian galectins.