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 alpha-P atom. Involved in the biosynthesis of lipid A, a phosphorylated glycolipid that anchors the lipooligosaccharide (LOS) to the outer membrane of the cell. Can functionally complement lpxH deficiency in E.coli. Overexpression of LpxG results in toxic accumulation of lipid X and profoundly reduces the infectivity of C.trachomatis. Can utilize UDP-2-N,3-O-bis((3R)-3-hydroxytetradecanoyl)-alpha-D-glucosamine as substrate in vitro, but the substrate is likely UDP-2-N-((3R)-3-hydroxyicosanoyl),3-O-(tetradecanoyl)-alpha-D-glucosamine in vivo. H2O + UDP-2,3-diacyl-alpha-D-glucosamine = 2,3-diacyl-alpha-D-glucosaminyl 1-phosphate + 2 H(+) + UMP Binds 2 divalent metal cations. Glycolipid biosynthesis; lipid IV(A) biosynthesis. Belongs to the metallophosphoesterase superfamily. LpxG family.