Analysis of the nucleotide sequence of a 1592 bp region of Acetobacter xylinum genomic DNA involved in acetan biosynthesis revealed the presence of an open-reading frame (aceM) encoding a protein of 449 amino acids with a molecular weight of 48.5 kDa. The deduced amino acid sequence of aceM displayed high homology to the protein sequences of genes encoding UDP-glucose dehydrogenase (UGDH) activities from other organisms. AceM is likely to encode the UGDH involved in the biosynthesis of UDP-glucuronic acid required for acetan biosynthesis.