Mechanism of enzymatic crosslinking of fibrinogen molecules

The mechanism of enzymatic covalent crosslinking of fibrinogen molecules under the effect of plasma transglutaminase (factor XIIIa) has been studied. Using the methods of elastic and dynamic light scattering combined with viscosimetry and electrophoresis of the reduced samples, it has been shown that fibrinogen oxidation strongly accelerates self-assembly of the covalently crosslinked fibrinogen polymers. IR-spectroscopy data indicate that the degree of fibrinogen oxidation positively correlates with the amount of ε/(γ-glu)lys isopeptide covalent bonds whose formation is catalyzed by the factor XIIIa. The results of this and our previous studies cast doubt on the widespread concept that native fibrinogen is the substrate for factor XIIIa. In our opinion, only structurally defective fibrinogen molecules that have undergone oxidative structural conversion in the D -domain region are involved in the enzymatic reaction leading to the formation of covalent ε/(γ-glu)lys isopeptide bonds and self-assembly of fibrinogen polymers.