Factor XIII or fibrin stabilizing factor is an enzyme (EC 2.3.2.13 (http://us.expasy.org/cgi-bin/nicezyme.pl?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.
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.
OMIM134570 (http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=134570) (A subunit) and OMIM134580 (http://www.ncbi.nlm.nih.gov/entrez/dispomim.cgi?id=134580) (B subunit)
Factor XIII deficiency (http://www.hemophilia.org/bdi/bdi_types11.htm)
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