Tissue Factor Pathway Inhibitor

Tissue factor pathway inhibitor regulates the extrinsic pathway.
The protein has three Kunitz domains; these are domains which can bind to and inhibit serine proteases.
The first Kunitz domain inhibits factor VIIa in the tissue factor:VIIa complex. The second Kunitz domain inhibits factor Xa.
The second Kunitz domain has been co-crystallized with trypsin, a serine protease related to factor X.

• Cyan = Trypsin
• Magenta = TFPI Kunitz domain
• Spacefill = Catalytic triad of trypsin (His57, Asp102, Ser195)

The TFP inhibitor blocks access to the active site of the protease

• Cyan = Trypsin
• Magenta = TFPI Kunitz domain
• Spacefill = Catalytic triad of trypsin (His57, Asp102, Ser195)

The TFP inhibitor blocks access to the active site of the protease