Hydrolyzes the pyrophosphate bond of UDP-2,3-diacylglucosamine to form 2,3-diacylglucosamine 1-phosphate (lipid X) and UMP by catalyzing the attack of water at the beta-P atom. Involved in the biosynthesis of lipid A, a phosphorylated glycolipid that anchors the lipopolysaccharide to the outer membrane of the cell. Can functionally complement lpxH deficiency in E.coli. Cannot use CDP-diacylglycerol as substrate. H2O + UDP-2-N,3-O-bis[(3R)-3-hydroxytetradecanoyl]-alpha-D-glucosamine = 2-N,3-O-bis[(3R)-3-hydroxytetradecanoyl]-alpha-D-glucosaminyl 1-phosphate + 2 H(+) + UMP To a lesser extent, can also use Mn(2+) or Co(2+). Inhibited by high concentrations of Cu(2+) and Zn(2+). Completely inhibited by EDTA in vitro. Optimum pH is 7-9. The activity is relatively constant between pH 6.5 and 9 but declines sharply below pH 6. Glycolipid biosynthesis; lipid IV(A) biosynthesis; lipid IV(A) from (3R)-3-hydroxytetradecanoyl-[acyl-carrier-protein] and UDP-N-acetyl-alpha-D-glucosamine: step 4/6. Homodimer. Consists of two domains: an N-terminal lipid X binding domain (LXD) attached by a flexible linker to a C-terminal catalytic domain (ICD). Binding of UDP-2,3-diacylglucosamine by LpxI induces a conformational switch that brings the catalytic domain close to the lipid-binding domain for specific recognition of the substrate and catalysis. LpxI generates the same products from the same substrate than LpxH but by a different hydrolytic mechanism. LpxH and LpxI share no sequence similarity and show a different taxonomic distribution. Belongs to the LpxI family.