Kallikrein (KLKB1) Protein

Plasma prekallikrein is a glycoprotein that participates in the surface-dependent activation of blood coagulation, fibrinolysis, kinin generation and inflammation. It is synthesized in the liver and secreted into the blood as a single polypeptide chain. Plasma prekallikrein is converted to plasma kallikrein by factor XIIa by the cleavage of an internal Arg-Ile bond. Plasma kallikrein therefore is composed of a heavy chain and a light chain held together by a disulphide bond. The heavy chain originates from the amino-terminal end of the zymogen and contains 4 tandem repeats of 90 or 91 amino acids. Each repeat harbors a novel structure called the apple domain. The heavy chain is required for the surface-dependent pro-coagulant activity of plasma kallikrein. The light chain contains the active site or catalytic domain of the enzyme and is homologous to the trypsin family of serine proteases. Plasma prekallikrein deficiency causes a prolonged activated partial thromboplastin time in patients. [provided by RefSeq, Jul 2008]

KLKB1: The enzyme cleaves Lys-Arg and Arg-Ser bonds. It activates, in a reciprocal reaction, factor XII after its binding to a negatively charged surface. It also releases bradykinin from HMW kininogen and may also play a role in the renin-angiotensin system by converting prorenin into renin. Defects in KLKB1 are the cause of prekallikrein deficiency (PKK deficiency); also known as Fletcher factor deficiency. This disorder is a blood coagulation defect. Belongs to the peptidase S1 family. Plasma kallikrein subfamily.

Protein type: Secreted; Secreted, signal peptide; Protease; EC 3.4.21.34

Chromosomal Location of Human Ortholog: 4q35

Cellular Component: extracellular space; extracellular region; plasma membrane

Molecular Function: protein binding; serine-type endopeptidase activity

Biological Process: extracellular matrix disassembly; fibrinolysis; extracellular matrix organization and biogenesis; positive regulation of fibrinolysis; zymogen activation; proteolysis; blood coagulation; blood coagulation, intrinsic pathway; Factor XII activation; plasminogen activation

Disease: Prekallikrein Deficiency