title: Direct evidence for Hageman factor (factor XII) activation by bacterial lipopolysaccharides (endotoxins).
abstract: Purified precursor Hageman factor has been demonstrated to bind to soluble bacterial lipopolysaccharide (LPS, endotoxin) isolated from Escherichia coli 0111:B4, and this complex has been shown to have the capacity to convert prekallikrein to its active form. In addition, LPS-activated Hageman factor substantially reduces clotting times in XII-deficient plasma. The capacity to activate Hageman factor has been demonstrated to reside in the lipid A region of the LPS molecule. Activation of Hageman factor by LPS contrasts with fluid-phase activation (e.g., by kallikrein or trypsin) in that no cleavage to lower molecular weight fragments occurs. High concentrations of LPS inhibit the activity of Hageman factor, probably by a direct LPS-Hageman factor interaction.
mesh_terms: D000818:Animals; D001777:Blood Coagulation; D004731:Endotoxins; D004789:Enzyme Activation; D004792:Enzyme Precursors; D004926:Escherichia coli / Q000276:immunology; D005174:Factor XII / Q000378:metabolism*; D006801:Humans; D007457:Iodine Radioisotopes; D007610:Kallikreins / Q000096:biosynthesis; D011135:Polysaccharides, Bacterial / Q000378:metabolism*; D011485:Protein Binding; D011817:Rabbits; D012475:Salmonella / Q000276:immunology
chemical_list: D004731:Endotoxins; D004792:Enzyme Precursors; D007457:Iodine Radioisotopes; D011135:Polysaccharides, Bacterial; D005174:Factor XII; D007610:Kallikreins