Effects on factor Xlla

Mechanism Heparin catalyzes the binding of antithrombin III (a serine protease inhibitor) to factors Ila, IXa, Xa, XIa, and Xlla, resulting in their rapid inactivation 4- Hepatic synthesis of vitamin K-dependent factors II, VII, IX, j X-—coumarins prevent 1 y-carboxylation by inhibiting vitamin K epoxide reductase no effect on factors already present. j In vivo effects only 1... 

One function of HK is to present the substrates of factor Xlla in a conformation that facilitates their activation [25, 26]. More difficult to explain is the effect of HK on the rate of factor XII activation in plasma since HK does not interact with factor XII, nor does it augment the activity of kaiiikrein. This effect seems to be largely indirect. First, HK is required for efficient formation of kaiiikrein in surface-activated plasma [26, 27]. Second, since kaiiikrein can disassociate from surface-bound... 

Bik inhibits the trypsin serine proteases through binding of either of its two Kunitz domains. Depending on the serine protease and the Kunitz domain involved, dissociation constants (K ) range from 0.03 to 800 pM [6, 28]. Bik fragmentation and glycation also effect strength and specificity of inhibition. For example, trypsin, chymotrypsin, kallikrein, plasmin, elastase, and cathepsin are inhibited at a A) of 0.03-3 pM, whereas Factors IXa, Xa, XIa, and Xlla are less inhibited with a A) of 15-800 pM. Protease inhibition is observed with both Kunitz domains except for Factors IXa and Xa that... 

---