Acyloxyacyl hydrolase
In enzymology, an acyloxyacyl hydrolase is an enzyme that catalyzes the chemical reaction
Hence, this enzyme has one substrate, the 3-acyl groups of bacterial lipopolysaccharides, and two products, and 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. Acyloxyacyl hydrolase is produced by monocyte-macrophages, neutrophils, dendritic cells, and renal cortical epithelial cells. It is a protein of Mr = ~60,000 that has two disulfide-linked subunits. The smaller subunit, of Mr = ~14,000, is a member of the SAPLIP family along with amoebopore, granulysin, acid sphingomyelinase, surfactant protein B, and the 4 sphingolipid activator proteins. The larger subunit, Mr = 50,000, 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.
