Structural Glycobiology Section, Center for Cancer Research Nanobiology Program, NCI-Frederick, Frederick, MD 21702, USA.
Curr Opin Struct Biol. 2010 Oct;20(5):536-42. doi: 10.1016/j.sbi.2010.07.004. Epub 2010 Aug 11.
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.
细胞表面糖链发挥着重要的细胞功能，它们是由糖基转移酶合成的。结构与功能研究表明，无脊椎动物β1,4-N-乙酰半乳糖胺基转移酶（β4GalNAc-T）和脊椎动物β1,4-半乳糖基转移酶 I（β4Gal-T1）的供体糖特异性通过单个氨基酸残基的变化相关联。β4Gal-T1 和α-多肽半乳糖基-N-乙酰氨基葡萄糖转移酶（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，无脊椎动物β4GalNAc-T 和αppGalNAc-T 的催化结构域可能来自一个共同的原始基因。当脊椎动物从无脊椎动物中出现时，决定无脊椎动物β4GalNAc-T 的供体糖特异性的氨基酸可能发生了突变，从而使该酶在脊椎动物中转化为β4Gal-T1。
