Fibrinopeptide A, human is a 16-residue short polypeptide cleaved from fibrinogen by thrombin. Fibrinopeptide A, human locates at the NH₂-termini of the Aα chain. In Vitro: The conversion of monomeric fibrinogen into polymeric fibrin is mediated by thrombin, which binds to the central region of fibrinogen and catalyzes cleavage of the 2 short peptides, the 16-residue fibrinopeptide A (FpA) and the 14-residue fibrinopeptide B (FpB), located at the NH₂-termini of the Aα and Bβ chains, respectively^[1]. In Vivo: Fibrinopeptide A (FPA) is a small polypeptide cleaved from fibrinogen by thrombin, has a short half-life, and is considered a sensitive biochemical marker of thrombin activity, fibrin generation, and ongoing thrombosis^[2].