Factor XII
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Hageman factor is a plasma protein now usually known as factor XII. It is part of the coagulation cascade and activates factor XI and prekallikrein. It is an enzyme (EC 3.4.21.38 (http://www.expasy.org/cgi-bin/nicezyme.pl?3.4.21.38)) of the serine protease (or serine endopeptidase) class.
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Genetics
The gene for factor XII is located on the tip of the long arm of the fifth chromosome (5q33-qter).
Deficiency
Hageman factor deficiency is a rare hereditary disorder with a prevalence of about one in a million, although it is a little more common among Asians. Deficiency does not cause excessive haemorrhage as the other coagulation factors make up for the it. It may increase the risk of thrombosis, due to inadequate activation of the fibrinolytic pathway.
History
Hageman factor was first discovered in 1955 when a routine preoperative blood sample of the 37-year-old railroad brakeman John Hageman was found to have prolonged clotting time in test tubes, even though he had no haemorrhagic symptoms. Hageman was then examined by Dr. Oscar Ratnoff who found that Mr. Hageman lacked a previously unidentified clotting factor. Dr. Ratnoff later found that the Hageman factor deficiency is autosomal recessive disorder, when examining several related people which had the deficiency. Paradoxically, pulmonary embolism contributed to Hageman's death after an occupational accident.
External link
| Cardiovascular system - Blood |
| Red blood cells - White blood cells - Platelets - Blood plasma |
| White blood cells |
| Granulocytes (Neutrophil granulocytes, Eosinophil granulocytes, Basophil granulocytes) - Lymphocytes - Monocytes |
| Coagulation |
| Coagulation factors: - Fibrin (I) - (Pro)thrombin (II) - FV - FVII - FVIII - FIX - FX - FXI - FXII - FXIII - HMWK - vWF - Tissue factor |
| Inhibitors: Antithrombin - Protein C - Protein S - Protein Z - ZPI - TFPI |
| Fibrinolysis: Plasmin - tPA/urokinase - PAI-1/2 - α2-AP - TAFI |