Coagulation factor XIII B chain (F13B) (F13B)

Coagulation factor XIII B chain (F13B) is a non-catalytic glycoprotein that serves as the essential carrier protein for the catalytic A-subunits in the blood, forming the heterotetrameric FXIII-A2B2 complex (UniProt: P05160). It is composed of ten Sushi domains, also known as complement control protein modules, and is synthesized primarily in the liver (NCBI Gene: 2165). The B-subunit's primary physiological role is to stabilize the A-subunit in circulation, preventing its premature degradation and extending its half-life from approximately 10 hours to 10 days (PMID: 28293116). It also acts as a regulatory molecule, modulating the rate of FXIII activation by thrombin and calcium during the final stages of the coagulation cascade. Genetic mutations in the F13B gene result in Factor XIII deficiency type I, a rare but severe bleeding disorder characterized by the depletion of both A and B subunits from the plasma (PMID: 15102357). Therapeutic management typically involves replacement therapy using plasma-derived FXIII concentrates containing the full A2B2 complex, such as Corifact, or recombinant A-subunit products like Catridecacog that associate with endogenous B-subunits upon administration (DrugBank: DB09014).

Other names

Factor XIII B subunitFibrin-stabilizing factor B subunitFXIII-BTransglutaminase B chainSushi domain-containing protein

The B-subunit acts as a carrier protein that stabilizes the catalytic A-subunit in plasma, protecting it from proteolytic degradation and regulating its activation by thrombin (PMID: 28293116).