UDP-glucose 4-epimerase (GalE) catalyzes the interconversion of UDP-glucose (UDP-Glc) and UDP-galactose (UDP-Gal) and/or the interconversion of UDP-N-acetylglucosamine (UDP-GlcNAc) and UDP-N-acetylgalactosamine (UDP-GalNAc) in sugar metabolism. GalEs belong to the short-chain dehydrogenase/reductase superfamily, use a conserved ‘transient keto intermediate’ mechanism and have variable substrate specificity. GalEs have been classified into three groups based on substrate specificity: group 1 prefers UDP-Glc/Gal, group 3 prefers UDP-GlcNAc/GalNAc, and group 2 has comparable activities for both types of the substrates. The phylogenetic relationship and structural basis for the specificities of GalEs revealed possible molecular evolution of UDP-hexose 4-epimerases in various organisms. Based on the recent advances in studies on GalEs and related enzymes, an updated view of their evolutional diversification is presented.

UDP-葡萄糖4-差向异构酶（大风）催化UDP-葡萄糖（UDP-GLC）和UDP-半乳糖（UDP-Gal的）和/或UDP-的相互的互Ñ乙酰氨基葡萄糖（UDP-GlcNAc的）和UDP- Ñ-乙酰半乳糖胺（UDP-GalNAc）在糖代谢中。GalEs 属于短链脱氢酶/还原酶超家族，使用保守的“瞬时酮中间体”机制并具有可变的底物特异性。GalEs 已根据底物特异性分为三组：第 1 组更喜欢 UDP-Glc/Gal，第 3 组更喜欢 UDP-GlcNAc/GalNAc，第 2 组对两种类型的底物具有相当的活性。GalEs 特异性的系统发育关系和结构基础揭示了 UDP-己糖 4-差向异构酶在各种生物中可能的分子进化。基于 GalEs 和相关酶研究的最新进展，提出了其进化多样化的最新观点。