Kininogen

Kininogen is a type of protein that plays a crucial role in the blood coagulation system and the kinin-kallikrein system. It is a precursor to kinin, a group of proteins that cause blood vessels to dilate and cause smooth muscle to contract.

Structure[edit | edit source]

Kininogen is a single-chain glycoprotein that is produced in the liver. It is composed of two types: high molecular weight kininogen (HMWK) and low molecular weight kininogen (LMWK). Both types are encoded by the same gene, but they differ in their post-translational modifications and functions.

Function[edit | edit source]

Kininogen serves as a precursor to kinin, which is released through the action of kallikrein, an enzyme that cleaves kininogen. Kinin, in turn, is a potent mediator of various physiological processes, including vasodilation, inflammation, and pain perception.

HMWK is involved in blood coagulation, acting as a cofactor for the assembly of the prekallikrein-Factor XII complex. LMWK, on the other hand, is primarily involved in the kinin-kallikrein system, leading to the production of bradykinin, a potent vasodilator.

Clinical significance[edit | edit source]

Alterations in the levels of kininogen can lead to various health conditions. For instance, reduced levels of HMWK can result in hereditary angioedema, a rare but serious condition characterized by episodes of severe swelling. On the other hand, elevated levels of kininogen have been associated with increased risk of thrombosis and cardiovascular disease.