Native factor P from human serum. Glycoprotein found in circulating blood plasma in dimeric, trimeric, and tetrameric forms with M.W. of ~92 kDa, ~138 kDa, and ~184 kDa, respectively. Present in normal human serum at about 20 µg/ml. Regulatory protein of the alternative pathway of complement activation. Accelerates complement activation by binding to and stabilizing the alternative pathway C3 and C5 convertase enzymes.
