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：1976
卷号：73
期号：5
页码：1591-1593
DOI：10.1073/pnas.73.5.1591
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Phenylalanine hydroxylase [phenylalanine 4-monooxygenase; EC 1.14.16.1 ; L-phenylalanine, tetrahydropteridine:oxygen oxidoreductase(4-hydroxylating)] isolated from rat liver is a phosphoprotein containing approximately 0.31 mumol of protein-bound phosphate per mumol of subunit (50,000 molecular weight). When the enzyme is further phosphorylated in the presence of ATP and a 3'5'-cyclic-AMP-dependent protein kinase (EC 2.7.1.37 ; ATP:protein phsophotransferase), an additional 0.7 mumol of phosphate per mumol of subunit is introduced, bringing the total phosphate content up to about 1 mumol/mumol of subunit. This phosphorylation of the enzyme in vitro is accompanied by a 2.6-fold increase in hydroxylase activity when the activity is assayed in the presence of tetrahydrobiopterin. Partial proteolytic digestion of phenylalanine hydroxylase, which previously had been shown to activate the enzyme 20- to 50-fold [Fisher, D.B. & Kaufman, S. (1973) J. Biol. Chem. 248, 4345-4353], removes almost all of the phosphate from the enzyme.
