An unknown D-tagatose 3-epimerase (DTE) containing a loIE domain was identified and cloned from Escherichia coli. This gene was subcloned into the prokaryotic expression vector pET-15b, and induced by IPTG in E. coli BL21 expression system. Through His-select gel column purification and fast-protein liquid chromatography, highly purified and stable DTE protein was produced. The molecular weight of the DTE protein was estimated to be 29.8 kDa. The latest 83 DTE sequences from public database were selected and analyzed by molecular clustering, multi-sequence alignment. DTEs were roughly divided into five categories. (C) 2015 Elsevier Inc. All rights reserved.