Janus kinase

Janus kinase (short JAK) is a family of intracellular tyrosine kinases, ranging from 120-140 kDa, that are involved in the signalling cascade of cytokines by associating with one of the cytokine receptors, for example, the interferon receptor.

The kinase was named after Janus, the Roman gatekeeper of heaven. He is described as having two faces. The kinase is named after him becauseite has two phosphate-transferring domains. The abbreviation JAK is sometimes interpreted as "just another kinase".

See also: JAK-STAT pathway