期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1980
卷号：77
期号：1
页码：92-96
DOI：10.1073/pnas.77.1.92
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Data demonstrating the direct phosphorylation of tyrosine hydroxylase [tyrosine 3-monooxygenase; L-tyrosine, tetrahydropteridine:oxygen oxidoreductase (3-hydroxylating), EC 1.14.16.2 ] purified from rat pheochromocytoma by ATP, Mg2+ and cyclic AMP-dependent protein kinase catalytic subunit are presented. The incorporation of phosphate is highly correlated with the activation of the hydroxylase when either the time of preincubation or the amount of protein kinase subunit is varied. The rate of phosphorylation of tyrosine hydroylase compares favorably with that of H1 histone, a known substrate of protein kinase. Lineweaver-Burk analysis of crude or purified rat pheochromocytoma tyrosine hydroxylase activity, as a function of pterin cofactor concentration, in the absence of ATP, Mg2+, and protein kinase catalytic subunit, yields a curvilinear relationship which can be resolved into two lines, suggesting two enzyme forms with different affinities for pterin cofactor. A fraction of the hydroxylase present in the tumor exists in the activated state, presumably due to the presence of ATP and endogenous protein kinase activity. When the solubl enzyme is activated by cyclic AMP, ATP, Mg2+, and protein kinase, virtually all of the enzyme is converted to the low Km state. We conclude that tyrosine hydroxylase is a substrate of cyclic AMP-dependent protein kinase in vitro and, presumably, in vivo.
