Besides its role in forming cell membranes, the lipid phosphatidylserine, or PS, also appears to activate the final step in the process of blood coagulation - the conversion of prothrombin to thrombin, the central enzyme of coagulation. Thrombin is needed both to encourage and then cut off clotting at a wound.
A report of the research appears in the online edition of the Journal of Biological Chemistry; print publication is slated for August. Senior author is Dr. Barry R. Lentz, professor of biochemistry and biophysics at the UNC School of Medicine.
Dr. Harold Roberts, Sarah Graham Kenan professor of medicine and pathology at the medical school and a renowned hematology expert, hailed the new results as "a major accomplishment in our understanding of blood coagulation which is essential to our understanding of blood clotting disorders that cause heart attacks and strokes, the major causes of mortality in the United States and the rest of the Western world."
Lentz said the new paper is the culmination of a series of reports from his laboratory countering a popular belief in the field about blood cell membranes' role in thrombin production. In that view, thrombin production occurs in a reaction occurring on the surface membranes of platelets, the blood cell responsible for clotting. Although Lentz, and then others, showed that membranes containing PS work best in thrombin formation, the popular view proposed no role for PS except that it is a negatively charged component of platelet membrane structure.
Lentz said the new findings unequivocally support a new view, that PS can activate conversion of prothrombin to thrombin in the absence of the platelet membrane surface. And it does so by triggering assembly of the enzyme complex, prothrombinase, whi
Contact: Les Lang
University of North Carolina School of Medicine