Acyloxyacyl Hydrolase

acyloxyacyl hydrolase
Acyloxyacyl hydrolase heterodimer, Human
Identifiers
EC number	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
Search 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

• "Deacylation of structurally diverse lipopolysaccharides by human acyloxyacyl hydrolase". J. Biol. Chem. 265 (27): 16444–9. 1990. PMID 2398058. 
• Hagen, F.; O'Hara PJ, Munford RS; characterization of recombinant human acyloxyacyl hydrolase, a leukocyte enzyme that deacylates bacterial lipopolysaccharides (1991). "Expression". Biochemistry 30 (34): 8415–8423. doi:10.1021/bi00098a020. PMID 1883828. 
• "Acyloxyacyl hydrolase, a leukocyte enzyme that deacylates bacterial lipopolysaccharides, has phospholipase, lysophospholipase, diacylglycerollipase, and acyltransferase activities in vitro". J. Biol. Chem. 267 (14): 10116–21. 1992. PMID 1577781. 
• "GDSL family of serine esterases/lipases". Prog. Lipid Res. 43: 534–552. 2004. doi:10.1016/j.plipres.2004.09.002. PMID 15522763. 
• "Biochemical transformation of bacterial lipopolysaccharides by acyloxyacyl hydrolase reduces host injury and promotes recovery". J Biol Chem 295 (51): 17842-1785. 2020. doi:10.1074/jbc.REV120.015254. PMID 33454018. 

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