Reaction: a lipid-linked O antigen + a lipid A-core oligosaccharide = a lipopolysaccharide + a polyisoprenyl diphosphate
Other name(s): waaL (gene name); surface polymer:lipid A-core ligase; rfaL (gene name)
Systematic name: lipid-linked O-antigen:lipid A-core oligosaccharide O-antigen transferase (configuration-inverting)
Comments: This Gram-negative bacterial enzyme attaches the polymerized O antigen molecule to the outer core region of the lipid A-core oligosaccharide, finalizing the biosynthesis of the lipopolysaccharide. Prior to the reaction the two substrates are attached to the periplasmic-facing side of the inner membrane, and the enzyme transfers the O-antigen from its polyprenyl diphosphate membrane anchor (usually ditrans,octacis-undecaprenyl diphosphate) to a terminal sugar of the lipid A-core oligosaccharide. Despite the popular name "ligase", the enzyme is not a real ligase, as the reaction does not involve the hydrolysis of a phosphate bond in a triphosphate. The enzyme is embedded in the inner membrane and often has 12 trans-membrane segments. It is a metal-independent inverting glycosyltransferase, and in some cases it can attach surface polymers other than O-antigens to the lipid A-core oligosaccharide.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, CAS registry number:
References:
1. MacLachlan, P.R., Kadam, S.K. and Sanderson, K.E. Cloning, characterization, and DNA sequence of the rfaLK region for lipopolysaccharide synthesis in Salmonella typhimurium LT2. J. Bacteriol. 173 (1991) 7151-7163. [PMID: 1657881]
2. Whitfield, C., Amor, P.A. and Koplin, R. Modulation of the surface architecture of gram-negative bacteria by the action of surface polymer:lipid A-core ligase and by determinants of polymer chain length. Mol. Microbiol. 23 (1997) 629-638. [PMID: 9157235]
3. Ruan, X., Loyola, D.E., Marolda, C.L., Perez-Donoso, J.M. and Valvano, M.A. The WaaL O-antigen lipopolysaccharide ligase has features in common with metal ion-independent inverting glycosyltransferases. Glycobiology 22 (2012) 288-299. [PMID: 21983211]
4. Ruan, X., Monjaras Feria, J., Hamad, M. and Valvano, M.A. Escherichia coli and Pseudomonas aeruginosa lipopolysaccharide O-antigen ligases share similar membrane topology and biochemical properties. Mol. Microbiol. 110 (2018) 95-113. [PMID: 30047569]