Prekallikrein Activator and Kallikrein in Acetone- and Kaolin-activated Rat Plasma

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Abstract
Activation of plasminogen-free rat citrated plasma (RCPL-P) with acetone/kaolin yielded BAEe[benzoyl argine esterase]-esterase activities of 0.6-0.8 U[units]/ml. Gel filtration demonstrated 1 single peak of BAEe-esterase activity (MW approximately 135,000) with a kininogenase-esterase ratio (3.3) close to that known for human plasma kallikrein (2.7). Similarly activated rat citrated plasma (RCPL) revealed on gel filtration an additional esterase peak (MW approximately 47,000) with a low kininogenase-esterase ratio (0.3), and should accordingly not be used for a BAEe-esterase assay of rat plasma kallikrein. Acetone activation of RCPL-P and of RCPL yielded prekallikrein activator (PKA) activites which were about doubled by treatment with kaolin to 1.9-2.1 and 3.5-4.2 PKA-U/ml, respectively. Gel filtration of acetone-activated RCPL-P or RCPL revealed 2 peaks of PKA activity, MW approximately 110,000 corresponding to activated factor XII (XIIa), and MW approximately 33,000 corresponding to XII fragments (XIIf). Kaolin-treatment of acetone-activated RCPL-P, but not RCPL, caused an extensive fragmentation of XIIa to the 4-6 times more active XIIf. The lower yield of PKA-activity in acetone/kaolin-activated RCPL-P, as compared with activated RCPL, seems to be due to the absence of a factor of significance for the activation of factor XII, which is not plasmin, plasma kallikrein or high MW kininogen.