Protein C degradation in vitro by neutrophil elastase

Purified protein C is completely degraded into small peptides by in vitro incubation with purified elastase. Protein C is a rather sensitive substrate as degradation is already accomplished by low elastase concentrations (molar enzyme-to-substrate ratio 1:510) and short incubation periods (5 min-60 min). Protein C in a PPSB coagulation factor concentrate is equally degraded and similar split products are detected by blotting techniques. The protein C activity (measured by a chromogenic substrate) is faster reduced by elastase than the protein C concentration (measured by an ELISA). Incubation of normal plasma with high elastase concentrations (5.7 nmol/ml plasma) results in reduction of the protein C band while no split products are detectable. The pathophysiologic significance of the effects of elastase on protein C remains to be elucidated.