Catalyzes the transfer of myristate from myristoyl-acyl carrier protein (ACP) to Kdo(2)-(lauroyl)-lipid IV(A) to form Kdo(2)-lipid A. Can probably also catalyze the transfer of myristate to Kdo(2)-(palmitoleoyl)-lipid IV(A) to form the cold-adapted Kdo(2)-lipid A. In vitro, can acylate Kdo(2)-lipid IV(A), but acylation of (KDO)2-(lauroyl)-lipid IV(A) is about 100 times faster. In vitro, can use lauroyl-ACP but displays a slight kinetic preference for myristoyl-ACP. dodecanoyl-(Kdo)2-lipid IVA + tetradecanoyl-[ACP] = alpha-Kdo-(2->4)-alpha-Kdo-(2->6)-lipid A + holo-[ACP] (9Z)-hexadecenoyl-(Kdo)2-lipid IVA + tetradecanoyl-[ACP] = ((9Z)-hexadecenoyl-tetradecanoyl)-(Kdo)2-lipid A + holo-[ACP] Glycolipid biosynthesis; KDO(2)-lipid A biosynthesis; KDO(2)-lipid A from CMP-3-deoxy-D-manno-octulosonate and lipid IV(A): step 4/4. Bacterial outer membrane biogenesis; lipopolysaccharide biosynthesis. Makes pentaacylated lipid A rather than the usual hexaacylated lipid A. Belongs to the LpxL/LpxM/LpxP family. LpxM subfamily. Was originally thought to be the membrane-bound lytic murein transglycosylase (MLT).