A non-receptor tyrosine kinase that is essential for the development, maturation, and signaling of B-LYMPHOCYTES. It contains an N-terminal zinc finger motif and localizes primarily to the PLASMA MEMBRANE and nucleus of B-lymphocytes. Mutations in the gene that encode this kinase are associated with X-LINKED AGAMMAGLOBULINEMIA.

Synonyms: Tyrosine Kinase, Bruton's, Brutons Tyrosine Kinase, Tyrosine Kinase, Agammaglobulinaemia, EC 2.7.10.2, Bruton Tyrosine Kinase, Bruton's Tyrosine Kinase, Agammaglobulinaemia Tyrosine Kinase, Kinase, Bruton's Tyrosine, B Cell Progenitor Kinase, Kinase, Agammaglobulinaemia Tyrosine