ENZYME entry: EC 2.4.99.26

Accepted Name

O-antigen ligase

Reaction catalysed

a lipid-linked O antigen + a lipid A-core oligosaccharide = a lipopolysaccharide + a polyisoprenyl diphosphate

Comment(s)

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.

Cross-references

BRENDA

EC2PDB

ExplorEnz

KEGG Ligand Database for Enzyme Nomenclature

IUBMB Enzyme Nomenclature

MEDLINE

MetaCyc

Rhea expert-curated reactions

UniProtKB/Swiss-Prot

P27243, WAAL_ECOLI

Q9HUG6, WAAL_PSEAE

P26471, WAAL_SALTY

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