Studies on the Enzymatic Activity of the Antihemophilic Factor (Factor VIII)

Summary

Preparations of normal human antihemophilic factor (AHF, factor VIII) obtained by continuous free electrophoresis in the “Elphor” apparatus, were investigated for enzymatic activity on various substrates. A number of enzymatic activities could be excluded by screening tests, performed with fraction I of Cohn. In some preparations esterase-activity was demonstrable on the substrates benzoyl-arginyl-ethylester (BAEE) and on glycerol tributyrate. There was, however, no correlation between these esterase-activities and the AHF-activity in the preparations. Moreover, the stability of the esterase at 4° C was much greater than the stability of the AHF-activity. We therefore assume that the AHF has no enzymatic activity on these substrates under the conditions of the tests. Attempts to activate AHF by calcium, magnesium or serum, were unsuccessful. Both esterase-activities were also present in fraction I of Cohn prepared from normal human citrated or resin plasma. The esterase-activity on BAEE is removed from resin plasma by adsorption to barium sulphate. The esterase-activity on glycerol tributyrate is not adsorbed.

^* This work was aided by a grant from the Netherlands Organisation for Pure Scientific Research (ZWO).

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