Desialylation of fibrinogen with neuraminidase. Kinetic and clotting studies.

The removal, with time, of sialic acid residues from human fibrinogen by neuraminidase, can be explained, as a result of a mathematical analysis, by the summation of two first order reactions with clearly different rate constants. Quantitative studies on the bound sialic acid to isolated fibrinogen chains, after reduction and alkylation of the partially desialylated fibrinogen, show that the fast reaction takes place with the sialic acid bound to the B beta chains. This indicates that the carbohydrate located in the gamma chains is somehow protected or less accessible to the enzyme. Coagulation with thrombin of desialylated fibrinogen shows that the aggregation rate increases linearly as the amount of sialic acid residues decreases, regardless of their location in the fibrinogen molecule.