In vitro phosphorylation of a purified preparation of bovine corpus striatal tyrosine hydroxylase

Tyrosine hydroxylase was purified from bovine striatum. The preparation yielded a single band upon electrophoresis under dissociating conditions in acid-urea polyacrylamide gels. Incubation of the purified enzyme with homogeneous catalytic subunit of cyclic AMP-dependent protein kinase produced an activation of tyrosine hydroxylase characterized by a several-fold increase in its affinity for reduced pteridine cofactor without a change in maximum velocity. Similar incubations utilizing [gamma-³²p]ATP showed that direct phosphorylation of tyrosine hydroxylase mediates this activation.