Prekallikrein

Prekallikrein (PK), also known as Fletcher factor, is an 85,000 Mr

Prekallikrein is homologous to factor XI, and similarly consists of four apple domains and a fifth, catalytic serine protease domain. The four apple domains create a disk-like platform around the base of the catalytic domain. However, unlike factor XI, prekallikrein does not form dimers.

Prekallikrein is activated to form kallikrein by factor XII cleavage of a bond homologous to the corresponding bond cleaved during factor XI activation.^[2]

Prekallikrein deficiency

Hereditary deficiencies in PK are very rare. They can cause a prolonged

Deficiencies in PK can also be acquired due to some disease states, such as

Although most cases of prekallikrein deficiency are asymptomatic, a few reports link severe prekallikrein deficiency with thrombotic phenomena and recurrent pregnancy loss. More recently, a case of prekallikrein deficiency was shown to be associated with severe mucosal bleeding.[3]

Discovery of prekallikrein

PK was initially described by Hathaway et al. in 1965 after encountering a Kentucky family who exhibited strikingly abnormal APTT results, but showed no bleeding symptoms. The family appeared to have a hereditary deficiency in an unknown coagulation factor, dubbed “Fletcher factor” after the family. In 1973 Kirk Wuepper determined that Fletcher factor and prekallikrein were the same.^[4]

References