Kallikrein activates prothrombin.
Kallikrein is a multitalented enzyme in hemostasis and inflammation. Normally, kallikrein is formed in intrinsic hemostasis and activates factor XII. A total of 10 microL of 0 to 100 microg/mL human plasma kallikrein in 6% human albumin-PBS were incubated with 90 microL 111.1 microg/mL prothrombin in 6% human albumin in absence and presence of 23 mM Ca(++). After 0 to 64 minutes (37 degrees C), 100 microL of 2.5 M arginine, pH 9, were added. Fifty microliters of 0.72 mM HD-CHG-Ala-Arg-pNA in 1.36 M arginine were added and increase in absorbance at 405 nm was determined. Within 8 minutes (37 degrees C), 1 microg/mL kallikrein, ie, 2.5% of the normal plasmatic prekallikrein concentration, generates approximately 3 mIU/mL thrombin in absence and 27 mIU/mL thrombin in presence of Ca(++). Kallikrein can directly activate prothrombin; there is a shortcut in the intrinsic hemostasis system that generates catalytic amounts of thrombin without following the known intrinsic clotting pathway.
Stief
Thomas W
TW
Department of Clinical Chemistry, University Hospital Marburg, Germany. thstief@med.uni-marburg.de
D001777:Blood Coagulation; D002118:Calcium; D006487:Hemostasis; D006801:Humans; D007202:Indicators and Reagents; D007610:Kallikreins / Q000502:physiology*; D008722:Methods; D011516:Prothrombin / Q000378:metabolism*; D013917:Thrombin / Q000096:biosynthesis
D007202:Indicators and Reagents; D011516:Prothrombin; D007610:Kallikreins; D013917:Thrombin; D002118:Calcium