Factor XIII or fibrin stabilizing factor is an enzyme (EC 2.3.2.13) of the blood coagulation system that crosslinks fibrin. 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. Factor XIII is activated by thrombin into factor XIIIa; its activation into Factor XIIIa requires calcium as a cofactor.

Enzyme

Factor XIII consists of twice two subunits (2 A and 2 B), the genes for which are on different chromosomes:

• A subunit (6p25-p24). The transglutaminase part; this adds an alkyl group to the nitrogen on a glutamine residue, which binds in turn with a lysine on the other chain.
• B subunit (1q31-q32.1). This has no clear enzymatic activity, and may serve as a carrier for the A subunit.

Role in disease

Factor XIII deficiency may occur very rarely, and can cause a severe bleeding tendency.

See also

• D-dimer

External links

• (A subunit) and OMIM 134580 (B subunit)
• Factor XIII deficiency