3-(acyloxy)acyl group of bacterial toxin [CPD:C11547];
3-hydroxyacyl group of bacterial toxin [CPD:C11548];
fatty acid [CPD:C00162]
The substrate is lipid A on the reducing end of the toxic lipopolysaccharide (LPS) of Salmonella typhimurium and related organisms. It consists of diglucosamine, beta-D-GlcN-(1-> 6)-D-GlcN, attached by glycosylation on O-6 of its non-reducing residue, phosphorylated on O-4 of this residue and on O-1 of its potentially reducing residue. Both residues carry 3-(acyloxy)acyl groups on N-2 and O-3. The enzyme from human leucocytes detoxifies the lipid by hydrolysing the secondary acyl groups from O-3 of the 3-hydroxyacyl groups on the disaccharide (LPS). It also possesses a wide range of phospholipase and acyltransferase activities [e.g. EC 220.127.116.11 (phospholipase A2), EC 18.104.22.168 (lysophospholipase), EC 22.214.171.124 (phospholipase A1) and EC 126.96.36.199 (phosphatidylinositol deacylase)], hydrolysing diacylglycerol and phosphatidyl compounds, but not triacylglycerols. It has a preference for saturated C12-C16 acyl groups.