Kininogens
Encyclopedia
Kininogens are proteins that are defined by their role as precursors for kinin
, but that also can have additional roles.
The two main types are:
They are both spliced from the same precursor.
A third type, T-kininogen, is found in rats but not humans.
Kinin
A kinin is any of various structurally related polypeptides, such as bradykinin and kallikrein. They are members of the autacoid family.They act locally to induce vasodilation and contraction of smooth muscle.It is a component of the kinin-kallikrein system....
, but that also can have additional roles.
The two main types are:
- High-molecular-weight kininogen, which is produced by the liver together with prekallikreinPrekallikreinPrekallikrein , also known as Fletcher factor, is a 85,000 Mr serine protease that complexes with High-molecular-weight kininogen. PK is the precursor of plasma kallikrein, which is a serine protease that activates kinins. PK is cleaved to produce kallikrein by activated Factor XII . -...
. It acts mainly as a cofactor on coagulation and inflammation, and has no intrinsic catalytic activity. These high molecular weight kininogens are cleaved into bradykininBradykininBradykinin is a peptide that causes blood vessels to dilate , and therefore causes blood pressure to lower. A class of drugs called ACE inhibitors, which are used to lower blood pressure, increase bradykinin further lowering blood pressure...
and kallidinKallidinKallidin is a bioactive kinin formed in response to injury from kininogen precursors through the action of kallikreins.Kallidin is a decapeptide that can be converted to bradykinin by the aminopeptidase enzyme....
by tissue and plasma kallikreins. - Low-molecular-weight kininogenLow-molecular-weight kininogenLow-molecular-weight kininogen is a form of kininogen, which has been identified in mice, guinea pigs, and whales.It is also found in humans....
, which is produced locally by numerous tissues, and secreted together with tissue kallikreinKallikreinKallikreins are a subgroup of serine proteases, enzymes capable of cleaving peptide bonds in proteins. In humans, plasma kallikrein has no known homologue, while tissue kallikrein-related peptidases encode a family of fifteen closely related serine proteases...
.
They are both spliced from the same precursor.
A third type, T-kininogen, is found in rats but not humans.