EC 2.3.1.243     
Accepted name: acyl-Kdo2-lipid IVA acyltransferase
Reaction: a fatty acyl-[acyl-carrier protein] + an α-Kdo-(2→4)-α-Kdo-(2→6)-(acyl)-[lipid IVA] = an α-Kdo-(2→4)-α-Kdo-(2→6)-(acyl)2-[lipid IVA] + an [acyl-carrier protein]
Glossary: Kdo = 3-deoxy-D-manno-oct-2-ulopyranosylonic acid
a lipid IVA = 2-deoxy-2-{[(3R)-3-hydroxyacyl]amino}-3-O-[(3R)-3-hydroxyacyl]-4-O-phospho-β-D-glucopyranosyl-(1→6)-2-deoxy-3-O-[(3R)-3-hydroxyacyl]-2-{[(3R)-3-hydroxyacyl]amino}-1-O-phospho-α-D-glucopyranose
an α-Kdo-(2→4)-α-Kdo-(2→6)-(acyl)-[lipid IVA] = 3-deoxy-α-D-manno-oct-2-ulopyranosyl-(2→4)-3-deoxy-α-D-manno-oct-2-ulopyranosyl-(2→6)-2-deoxy-2-{[(3R)-3-(acyloxy)acyl]amino}-3-O-[(3R)-3-hydroxyacyl]-4-O-phospho-β-D-glucopyranosyl-(1→6)-2-deoxy-3-O-[(3R)-3-hydroxyacyl]-2-{[(3R)-3-hydroxyacyl]amino}-1-O-phosphono-α-D-glucopyranose
an α-Kdo-(2→4)-α-Kdo-(2→6)-(acyl)2-[lipid IVA] = 3-deoxy-α-D-manno-oct-2-ulopyranosyl-(2→4)-3-deoxy-α-D-manno-oct-2-ulopyranosyl-(2→6)-2-deoxy-2-{[(3R)-3-(acyloxy)acyl]amino}-3-O-[(3R)-3-(acyloxy)acyl]-4-O-phospho-β-D-glucopyranosyl-(1→6)-2-deoxy-3-O-[(3R)-3-hydroxyacyl]-2-{[(3R)-3-hydroxyacyl]amino}-1-O-phospho-α-D-glucopyranose
Other name(s): lpxM (gene name); MsbB acyltransferase; myristoyl-[acyl-carrier protein]:α-Kdo-(2→4)-α-Kdo-(2→6)-(dodecanoyl)-lipid IVA O-myristoyltransferase; tetradecanoyl-[acyl-carrier protein]:dodecanoyl-Kdo2-lipid IVA O-tetradecanoyltransferase; lauroyl-Kdo2-lipid IVA myristoyltransferase
Systematic name: fatty acyl-[acyl-carrier protein]:α-Kdo-(2→4)-α-Kdo-(2→6)-(acyl)-[lipid IVA] O-acyltransferase
Comments: The enzyme is involved in the biosynthesis of the phosphorylated outer membrane glycolipid lipid A. It transfers an acyl group to the 3-O position of the 3R-hydroxyacyl already attached at the 2-O position of the non-reducing glucosamine molecule. The enzyme from the bacterium Escherichia coli is specific for myristoyl (C14) acyl groups, giving the enzyme its previous accepted name. However, enzymes from different species accept highly variable substrates.
References:
1.  Clementz, T., Zhou, Z. and Raetz, C.R. Function of the Escherichia coli msbB gene, a multicopy suppressor of htrB knockouts, in the acylation of lipid A. Acylation by MsbB follows laurate incorporation by HtrB. J. Biol. Chem. 272 (1997) 10353–10360. [PMID: 9099672]
2.  Dovala, D., Rath, C.M., Hu, Q., Sawyer, W.S., Shia, S., Elling, R.A., Knapp, M.S. and Metzger, L.E., 4th. Structure-guided enzymology of the lipid A acyltransferase LpxM reveals a dual activity mechanism. Proc. Natl. Acad. Sci. USA 113 (2016) E6064–E6071. [PMID: 27681620]
[EC 2.3.1.243 created 2014, modified 2021]