Low molecular weight kininogen, also known as LMWK or prekallikrein, is a glycoprotein found in the human blood plasma. It is a vital component of the kinin system, which regulates various biological processes, including blood clotting, inflammation, and blood pressure regulation.
LMWK is synthesized primarily in the liver and released into the bloodstream, where it circulates as an inactive precursor. Upon activation, it plays a crucial role in initiating the coagulation cascade and the production of bradykinin, an important peptide involved in vasodilation and inflammation.
In the clotting pathway, LMWK serves as a cofactor for the activation of factor XII, also known as Hageman factor. When factor XII comes into contact with negatively charged surfaces, it stimulates the conversion of prekallikrein to kallikrein, an enzyme that cleaves high molecular weight kininogen. This split leads to the formation of bradykinin, which stimulates vasodilation, increases blood vessel permeability, and causes smooth muscle contraction.
Low molecular weight kininogen also contributes to the regulation of blood pressure by interacting with other proteins in the renin-angiotensin system. It binds to angiotensin-converting enzyme (ACE), preventing its interaction with angiotensin I and limiting the production of angiotensin II, a potent vasoconstrictor.
Overall, low molecular weight kininogen plays a crucial role in various physiological processes, including blood clotting, inflammation, and blood pressure regulation. Dysfunctions in its production or activity can lead to disorders such as hereditary angioedema or abnormal clotting conditions.
