Donlon J, Kaufman S
J Biol Chem. 1980 Mar 10;255(5):2146-52.
The two major forms of rat liver phenylalanine hydroxylase have been resolved by calcium phosphate chromatography and have been highly purified. These different forms of the enzyme contain dissimilar amounts of endogenous protein-bound phosphate. The hydroxylase activity of these forms, as assayed in the presence of tetrahydrobiopterin, can be differentially stimulated by treatment with Mg2+, ATP, cyclic AMP, and protein kinase, leading to the production of a chromatographically distinct species. In the presence of [gamma-32P]ATP, activation is accompanied by differential incorporation of 32P into the subunits (Mr = 50,000) of the two enzyme forms leading to a new form which contains 1 mol of phosphate/subunit. In addition, phosphorylation in vitro eliminates the electrophoretic heterogeneity displayed by the isolated forms. These data show that the multiple forms and electrophoretic heterogeneity of phenylalanine hydroxylase are correlated with the degree of phosphorylation and also provide further evidence for the regulation of this enzyme by phosphorylation and dephosphorylation.
大鼠肝脏苯丙氨酸羟化酶的两种主要形式已通过磷酸钙层析分离并得到高度纯化。这些不同形式的酶含有不同量的内源性蛋白质结合磷酸盐。在四氢生物蝶呤存在下测定时，这些形式的羟化酶活性可通过用Mg2+、ATP、环磷酸腺苷和蛋白激酶处理而受到不同程度的刺激，从而产生一种色谱上不同的物种。在[γ-32P]ATP存在下，激活伴随着32P以不同方式掺入两种酶形式的亚基（Mr = 50,000）中，形成一种新的形式，即每个亚基含有1摩尔磷酸盐。此外，体外磷酸化消除了分离形式所显示的电泳异质性。这些数据表明，苯丙氨酸羟化酶的多种形式和电泳异质性与磷酸化程度相关，也为该酶通过磷酸化和去磷酸化进行调节提供了进一步的证据。
