Acyloxyacyl hydrolase

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acyloxyacyl hydrolase
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Acyloxyacyl hydrolase heterodimer, Human
Identifiers
EC no. 3.1.1.77
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Gene Ontology AmiGO / QuickGO
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PMC articles
PubMed articles
NCBI proteins

The enzyme acyloxyacyl hydrolase (EC 3.1.1.77, AOAH) was discovered because it catalyzes the reaction

3-(acyloxy)acyl group of bacterial toxin + H2O = 3-hydroxyacyl group of bacterial toxin + a fatty acid

The enzyme removes from lipid A the secondary acyl chains that are needed for lipopolysaccharides to be recognized by the MD-2--TLR4 receptor on animal cells. This reaction inactivates the lipopolysaccharide (endotoxin); the tetraacyl lipid A product can inhibit LPS signaling. Acyloxyacyl hydrolase is produced by monocyte-macrophages, neutrophils, dendritic cells, NK cells, ILC1 cells, and renal cortical tubule cells. It is a protein of about 60 kDa that has two disulfide-linked subunits. The smaller subunit, of about 14 kDa (including glycosylation), is a member of the SAPLIP (saposin-like protein) family along with amoebapore, granulysin, acid sphingomyelinase, surfactant protein B, and the 4 sphingolipid activator proteins (saposins). The larger subunit, of 50 kDa, contains the active site serine and the other elements of the His-Asp-Ser triad; AOAH is a GDSL lipase that has activity toward certain glycerolipids in addition to its presumed major in vivo substrate, LPS. Also see "AOAH".

References