Dephosphorylation of purified brain tyrosine hydroxylase by rat striatal extracts

Tyrosine hydroxylase (TH) was purified from bovine brain and enzymatically phosphorylated in vitro. Radioactively phosphorylated TH was dephosphorylated by rat tissue extracts. Of tissues examined, rat corpus striatal extracts were highest in specific activity in the TH dephosphorylating assay. Phosphorylated histone did not inhibit dephosphorylation of TH by rat striatal extracts. The thermal decay of dephosphorylating activity of rat striatal extracts varied with substrate, with TH dephosphorylating activity most unstable of the activities assayed. The results suggest that TH can be enzymatically dephosphorylated and that, in corpus striatum, this process differs quantitatively from the dephosphorylation of phosphohistone and phosphoprotamine.