In the genome annotation of Escherichia coli MG1655, the orf382 (1,149 bp) is designated as a gene encoding an alcohol dehydrogenase that may be Fe-dependent. In this study, the gene was amplified from the genome by PCR and overexpressed in Escherichia coli BL21(DE3). The recombinant $6{ imes}$His-tag protein was then purified and characterized. In an enzymatic assay using different hydroxyl-containing substrates (n-butanol, $small{L}$-threonine, ethanol, isopropanol, glucose, glycerol, $small{L}$-serine, lactic acid, citric acid, methanol, or $small{D}$-threonine), the enzyme showed the highest activity on $small{L}$-threonine. Characterization of the mutant constructed using gene knockout of the orf382 also implied the function of the enzyme in the metabolism of $small{L}$-threonine into glycine. Considering the presence of tested substrates in living E. coli cel ls and previous literature, we believed that the suitable nomenclature for the enzyme should be an $small{L}$-threonine dehydrogenase (LTDH). When using $small{L}$-threonine as the substrate, the enzyme exhibited the best catalytic performance at $39^{circ}C$ and pH 9.8 with $NAD^+$ as the cofactor. The determination of the Km values towards $small{L}$-threonine (Km = $11.29{mu}M$), ethanol ($222.5{mu}M$), and n-butanol ($8.02{mu}M$) also confirmed the enzyme as an LTDH. Furthermore, the LTDH was shown to be an ion-containing protein based on inductively coupled plasma-atomic emission spectrometry with an isoelectronic point of pH 5.4. Moreover, a circular dichroism analysis revealed that the metal ion was structurally and enzymatically essential, as its deprivation remarkably changed the ${alpha}$-helix percentage (from 12.6% to 6.3%).