UDP-3-O-[3-hydroxymyristoyl] glucosamine N-acyltransferase (EC 2.3.1.-) catalyses an early step in lipid A biosynthesis: UDP-3-O-(3-hydroxytetradecanoyl)glucosamine + (R)-3-hydroxytetradecanoyl- [acyl carrier protein] -> UDP-2,3-bis(3-hydroxytetradecanoyl)glucosamine + [acyl carrier protein] [1]. Members of this family also contain a hexapeptide repeat (Pfam:PF00132). This family constitutes the non-repeating region of LPXD proteins.

1: The firA gene of Escherichia coli encodes UDP-3-O-(R-3-hydroxymyristoyl)-glucosamine N-acyltransferase. The third step of endotoxin biosynthesis. Kelly TM, Stachula SA, Raetz CR, Anderson MS; J Biol Chem 1993;268:19866-19874. PMID:8366125