Dephosphorylation of the lipid A moiety of Escherichia coli lipopolysaccharide by mouse macrophages.

An Escherichia coli deep rough lipopolysaccharide (LPS), biosynthetically labeled with 32PO4 and [3H]glucosamine, was used to study dephosphorylation of the lipid A moiety by murine macrophages. Over a 48-h incubation period, the macrophages removed approximately two-thirds of the 32P from [3H32P]LPS that was added to the culture medium. The LPS-derived phosphate was incorporated into cell components (e.g., phospholipids), as well as released from the cells. Cell lysates were also able to remove phosphate from [3H32P]LPS. The phosphatase activity was optimal at acidic pH and was greatly reduced by 10 mM sodium fluoride or heating at 80 degrees C. There was no evident difference in the LPS-dephosphorylating ability of macrophages from LPS-responsive and -hyporesponsive mice. The results indicate that murine macrophages dephosphorylate the lipid A moiety of deep rough E. coli LPS and raise the possibility that enzymatic dephosphorylation may modify LPS bioactivity.