细胞表面聚糖发挥重要的细胞功能并且通过糖基转移酶合成。结构和功能研究表明,无脊椎动物β1,4-N-乙酰-冰胺基转移酶(β4GalNAc-T)和脊椎动物β1,4-半乳糖基转移酶I(β4Gal-T1)的供体糖特异性与单个氨基酸残基的变化有关。β4Gal-T1和α-多肽基-GalNAc-T(αppGalNAc-T)的催化结构域晶体结构的比较表明,它们的蛋白质结构和序列相似。因此,似乎无脊椎动物β4GalNAc-T和αppGalNAc-T的催化结构域可能是从常见的原始基因中出现的。当脊椎动物从无脊椎动物中出现时,决定无脊椎动物β4GalNAc-T供体糖特异性的氨基酸可能已经突变,从而在脊椎动物中将酶转化为β4Gal-T1。
Cell surface glycans play important cellular functions and are synthesized by
glycosyltransferases. Structure and function studies show that the donor sugar specificity of the invertebrate β1,4-N-acetyl-glactosaminyltransferase (β4GalNAc-T) and the vertebrate β1,4-galactosyltransferase I (β4Gal-T1) are related by a single amino acid residue change. Comparison of the catalytic domain crystal structures of the β4Gal-T1 and the α-polypeptidyl-GalNAc-T (αppGalNAc-T) shows that their protein structure and sequences are similar. Therefore, it seems that the invertebrate β4GalNAc-T and the catalytic domain of αppGalNAc-T might have emerged from a common primordial gene. When vertebrates emerged from invertebrates, the amino acid that determines the donor sugar specificity of the invertebrate β4GalNAc-T might have mutated, thus converting the enzyme to a β4Gal-T1 in vertebrates.