Factor XIII is a transglutaminase that circulates in the plasma as a heterotetramer of two catalytic A subunits and two carrier B subunits. When thrombin has converted fibrinogen to fibrin, the latter forms a proteinaceous network in which every E-unit is crosslinked to only one D-unit. When someone births a insufficiency of Factor XIII, the tenuously formed clot will eventually break down and cause recurrent bleeds. The prolonged bleeding that is associated with Factor XIII constitutes usually connected with trauma. Among severe patients there is a high risk of head bleeds with or without trauma. Bleeding immediately after surgery is usually not excessive, but can be stayed. Charwomen who belong untreated danger spontaneous abortion.
Factor XIII is activated by thrombin into factor XIIIa; its activation into Factor XIIIa requires calcium every bit a cofactor. A cleavage by thrombin between residue Arg37 and Gly38 on the N-terminus of the A subunit, leads to the departure of the activation peptide (MW 4000 da). In the presence of calcium the carrier subunits dissociate from the catalytic subunits, leading to a 3D change in conformation of factor XIII and hence the exposure of catalytic cysteine residue. Upon activation by thrombin, divisor XIIIa dissembles on duty fibrin to form γ-glutamyl-Є-lysyl amide cross links between fibrin corpuscles to form an insoluble clot.
There have been more than 60 FXIII mutations identified in the current literature. In addition, single nucleotide polymorphisms have been described, some of which have been shown to affect FXIII activity, contributing further to the heterogeneity in patient presentation and severity of clinical symptoms. Although there is a lifelong risk of bleeding, the prognosis is excellent when current prophylactic treatment is available using cryoprecipitate or plasma-derived FXIII contract.
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