or fibrin stabilizing factor is an enzyme 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
FXIII is known also as Laki-Lorand factor, after the scientists
who first proposed its existence in 1948. A 2005 conference
recommended standardization of nomenclature. Zymogene factor
XIII is a 320000 Mr glycoprotein tetramer consisting 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. The
molecular weight of the A chain is approximately 83000. - B
subunit (1q31-q32.1). This has no clear enzymatic activity, and
may serve as a carrier for the A su