Abstract: The solution structure and function of human coagulation factor X (FX) were studied to understand the key structural elements of the enzyme form during activation. FX is a vitamin K-dependent plasma glycoprotein, composed of light and heavy chains, and plays a central role in the coagulation cascade. The calcium-rich γ-carboxyglutamic acid domain is responsible for binding to the membrane, an important step in the coagulation process. After activation, the serine protease domain undergoes a significant relocation, forming a compact multidomain. The S1-specific pocket largely determines the functional activities that activate FX. The enzyme-producing form of FX is more extensive than the active form. The enzyme-producing and activated forms of FX have different conformations in the serine protease domain.

Key words: factor Ⅹ, factor Xa, serine protease domain, γ-carboxyglutamic acid domain, differences