[Tyrosine hydroxylase of the blood leukocytes]

Tyrosine hydroxylase activity has been established in blood plasma leucocytes of rat, cat and man. Tyrosine precursors and some nuclear erythroid cells. GFU-GM did hydroxylase activity in leucocytes shows the Km for tyrosine inhibited by high concentrations of L6 tyrosine (substrate inhibition), alpha-methyl-para-tyrosine dopamine. The kinetic properties of leucocyte tyrosine hydroxylase are qualitatively similar to the properties of brain tyrosine hydroxylase.