Activation of Tyrosine Hydroxylase in Cultured Bovine

Abstract: We have identified a 5dkilodalton protein in cultured bovine adrenal chromaffin cells that is phos-phorylated when catecholamine secretion is stimulated. Immunodetection on Western blots from both one- and two-dimensional polyacrylamide gels indicated that this protein was tyrosine hydroxylase, the rate-limiting en-zyme in catecholamine biosynthesis. Two-dimensional polyacrylamide gel electrophoresis of proteins from un-stimulated cells revealed small amounts of phosphory-lated protein with a molecular weight of 56K and PI values of 6.37 and 6.27 which were subunits of tyrosine hydroxylase. Nicotinic stimulation of chromaffh cells caused the phosphorylation of three proteins of 56 kilo-daltons with PI values of approximately 6.37, 6.27, and 6.15 which were tyrosine hydroxylase. The immuno