THE EFFECT OF EXTRACELLULAR PROTEASES FROM GRAM-NEGATIVE BACTERIA ON THE INTERACTION OF VON WILLEBRAND FACTOR WITH HUMAN-PLATELETS

  • 1 January 1981
    • journal article
    • research article
    • Vol. 97  (3) , 379-389
Abstract
FWP [fixed washed human platelets] are usually stable for several mo. In less than a wk, one lot of FWP lost its ability to aggregate with bovine PAF [platelet-aggregating factor] or human vWF [von Willebrand factor] plus ristocetin. Initial experiments suggested that the aggregability loss was caused by contamination of the FWP with an extracellular protease of Serratia marcescens. Highly purified protease preparations from the culture filtrates of S. marcescens (SP), as well as from two strains of Pseudomonas aeruginosa, destroyed FWP aggregability as a function of time and concentration. On the basis of azocasein units, the SP was found to be at least 8 times more potent against FWP as a substrate than either of the P. aeruginosa proteases. The SP effect on FWP aggregability was inhibited by prior EDTA treatment and was restored by addition of Zn2+ in slight molar excess. Purified PAF, but not dilutions of bovine plasma, lost all PAF activity when incubated with SP. SP-treated FWP would still aggregate with 10 .mu.g/ml polylysine. SP digestion of FWP was more selective than digestion with trypsin or chymotrypsin, on the basis of both the polyacrylamide gel electrophoresis pattern and the protein amount in the platelet digest supernatant. SP does not aggregate fresh washed platelets or initiate the release reaction but renders them unaggregable with vWF. SP and related proteases may be useful in the study of platelet membranes.