Characterization of the sites phosphorylated on tyrosine hydroxylase by Ca2+ and phospholipid‐dependent protein kinase, calmodulin‐dependent multiprotein kinase and cyclic AMP‐dependent protein kinase

Abstract

Tyrosine hydroxylase purified from rat pheochromocytoma is phosphorylated rapidly by the Ca²⁺‐ and phospholipid‐dependent protein kinase (protein kinase C) purified from rat or sheep brain. Phosphorylation was stimulated 14‐fold by Ca²⁺ and phosphatidylserine and occurred at a rate comparable with that of the phosphorylation of histone H1. The phospholipid‐dependent protein kinase phosphorylates a single site which is identical to that phosphorylated by cyclic AMP‐dependent protein kinase and to the secondary site of phosphorylation by the calmodulin‐dependent multiprotein kinase. The implications of these results with respect to the regulation of catecholamine biosynthesis in adrenal medulla are discussed.