Catalyzes the N-acylation of UDP-3-O-(hydroxytetradecanoyl)glucosamine using 3-hydroxytetradecanoyl-ACP as the acyl donor. Is involved in the biosynthesis of lipid A, a phosphorylated glycolipid that anchors the lipopolysaccharide to the outer membrane of the cell. Prefers (3R)-3-hydroxytetradecanoyl-ACP over (3R)-3-hydroxyhexadecanoyl-ACP as the acyl donor in vitro, which is consistent with the structure of E.coli lipid A that contains over 95% (R)-3-hydroxytetradecanoate at the 2 and 2' positions. a (3R)-hydroxyacyl-[ACP] + a UDP-3-O-[(3R)-3-hydroxyacyl]-alpha-D-glucosamine = a UDP-2-N,3-O-bis[(3R)-3-hydroxyacyl]-alpha-D-glucosamine + H(+) + holo-[ACP] (3R)-hydroxytetradecanoyl-[ACP] + UDP-3-O-[(3R)-3-hydroxytetradecanoyl]-alpha-D-glucosamine = H(+) + holo-[ACP] + UDP-2-N,3-O-bis[(3R)-3-hydroxytetradecanoyl]-alpha-D-glucosamine Inhibited by divalent cations such as Ca(2+) and Mg(2+). kcat is 23 sec(-1). Glycolipid biosynthesis; lipid IV(A) biosynthesis; lipid IV(A) from (3R)-3-hydroxytetradecanoyl-[acyl-carrier-protein] and UDP-N-acetyl-alpha-D-glucosamine: step 3/6. Homotrimer. Belongs to the transferase hexapeptide repeat family. LpxD subfamily. Was originally thought to be involved in transcription.