Hemostasis

Intrinsic Pathway

Damaged Surface

Definitions

Kallikrein is a type of enzyme known as a serine protease, which means it can cleave peptide bonds in proteins. There are two main types of kallikreins in the human body:

Plasma Kallikrein: This is involved in the regulation of blood pressure and inflammation. It is synthesized as an inactive precursor called prekallikrein, which is activated by other factors in the blood 1.
Tissue Kallikreins: These are found throughout the body and have various physiological roles, including blood pressure regulation, semen liquefaction, and skin desquamation (shedding of the outer skin layer)1 2.

Kallikreins are also involved in the kinin–kallikrein system, which plays a role in inflammation, blood pressure control, coagulation, and pain 2.

High-Molecular-Weight Kininogen (HMWK) is a crucial protein in the intrinsic pathway of blood coagulation. It acts as a cofactor, meaning it helps other proteins in the pathway function properly. Here are some key points about HMWK:

Role in Coagulation: HMWK is involved in the initiation of the intrinsic pathway, which is also known as the contact activation pathway. It works alongside Factor XII, Factor XI, and prekallikrein 1 2.
Activation Process: When blood comes into contact with negatively charged surfaces, such as collagen exposed by injury, HMWK helps activate Factor XII (Hageman factor). This, in turn, activates Factor XI, leading to a cascade of reactions that result in blood clot formation 2 3.
Bradykinin Generation: HMWK is also a precursor to bradykinin, a peptide that causes blood vessels to dilate (widen), which can help regulate blood pressure and inflammation 1.