   3.1.1.77 | 3-(acyloxy)acyl group of bacterial toxin + H2O = 3-hydroxyacyl group of bacterial toxin + a fatty acid |
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 ist 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 3.1.1.4, phospholipase A2, EC 3.1.1.5, lysophospholipase, EC 3.1.1.32, phospholipase A1 and EC 3.1.1.52, phosphatidylinositol deacylase, hydrolysing diacylglycerol and phosphatidyl compounds, but not triacylglycerols. It has a preference for saturated C12-C16 acyl groups |
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