Summary
The effect of enzymatic removal of sialic acid residues on the functional properties
of human protein C was examined. The rates of activation of native and asialo protein
C were identical using either the thrombin thrombomodulin complex or the snake venom
activator, protac. Desialylated activated protein C (APC) was, two-three-fold more
active than native protein C, both as an anticoagulant and in its ability to hydrolyze
chromogenic substrates. The potentiating effect of the desialylation was confirmed
by initially fully activating protein C followed by the desialylation process. In
these studies, a two-three-fold enhancement in the activity of the protein was observed
which paralleled the extent of the desialylation. The activity of asialo-protein C
was completely abolished by monoclonal and polyclonal antiprotein C antibodies, confirming
that the effect was mediated by APC. Our studies suggest that the sialic acid component
of protein C is not essential for the expression of APC activity but may act to modulate
the function of the protein.
Keywords
Protein C - Coagulation - Sialic acid
