Bacillus subtilis 168 EpsM (UniProt id P71063) has been electronically annotated as putative acetyltransferase in the UniProt database. The gene epsM was cloned and overexpressed in E. coli with an N-terminal GST tag. The purified fusion protein was shown by absorption spectroscopy, autoradiography and reverse phase HPLC to catalyse the conversion of UDP-2,4,6-trideoxy-2-acetamido-4-amino glucose to UDP-2,4,6-trideoxy-2,4-diacetamido glucose, commonly known as N,N'-diacetylbacillosamine, using acetyl coenzyme A as the donor substrate. His146 was shown by site-directed mutagenesis to be essential for acetyltransferase activity. It is hypothesized that EpsC (NAD + dependent UDP GIcNAc 4,6-dehydratase), EpsN (PLP dependent aminotransferase) and EpsM, all of which are part of the eps operon, are involved in the biosynthesis of N,N'-diacetylbacillosamine. (C) 2018 Elsevier Inc. All rights reserved.