Brain striatal tyrosine hydroxylase: Activation of the enzyme by cyclic AMP-independent phosphorylation

Tyrosine hydroxylase has been purified from bovine striatum to apparent homogeneity as judged by electrophoresis under dissociating conditions. Incubation of the enzyme with an adenosine 3′:5′-mono-phosphate-independent protein kinase, highly purified from rat brain, and [γ-³²p]ATP Mg⁺⁺ resulted in phosphorylation and activation of tyrosine hydroxylase. The results suggest that the depolarization-induced activation of the enzyme which occurs in vivo may be mediated by a mechanism not involving changes in cyclic nucleotide levels.