Phosphorylation of Phenylalanine Hydroxylase Increases the Rate Constant for Formation of the Activated Conformation of the Enzyme.
Phosphorylation of Phenylalanine Hydroxylase Increases the Rate Constant for Formation of the Activated Conformation of the Enzyme.
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DOI：
10.1021/acs.biochem.8b00919
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发表时间：
2018-11-06
期刊：
影响因子：
2.9
通讯作者：
Fitzpatrick PF
中科院分区：
文献类型：
--
作者：
Khan CA;Fitzpatrick PF
肝脏苯丙氨酸羟化酶 (PheH) 是一种由苯丙氨酸激活的变构酶。该酶也被蛋白激酶 A 磷酸化，但磷酸化的影响尚不清楚。最近的结构研究（Meisburger et al. (2016) J. Amer. Chem. Soc. 138, 6506–6516）支持一种模型，其中酶的激活涉及调节域的二聚化，从而在二聚体界面处创建苯丙氨酸的变构位点。这种构象变化还会导致蛋白质荧光的变化，可用于监测激活。 PheH 的激活动力学在苯丙氨酸浓度范围内是双相的。这些数据通过一个模型得到了很好的描述，该模型涉及静止形式和激活构象之间的初始平衡，激活构象形成的平衡常数L的值等于0.007，随后两个苯丙氨酸分子结合。磷酸化通过增加静息形式向活化形式转化的速率常数，使 L 增加 10 倍。该结果为之前的结构模型提供了功能支持，确定了磷酸化对酶的具体影响，并合理化了磷酸化后蛋白质结构没有变化的主要结论。
Liver phenylalanine hydroxylase (PheH) is an allosteric enzyme that is activated by phenylalanine. The enzyme is also phosphorylated by protein kinase A, but the effects of phosphorylation are unclear. Recent structural studies (Meisburger et al. (2016) J. Amer. Chem. Soc. 138, 6506–6516) support a model in which activation of the enzyme involves dimerization of the regulatory domains, creating the allosteric site for phenylalanine at the dimer interface. This conformational change also results in a change in the fluorescence of the protein that can be used to monitor activation. The kinetics of activation of PheH are biphasic over a range of phenylala-nine concentrations. These data are well-described by a model involving an initial equilibrium between the resting form and the activated conformation, with a value of the equilibrium constant for formation of the activated conformation, L, equal to 0.007, followed by binding of two molecules of phenylalanine. Phosphorylation increases L 10-fold by increasing the rate constant for conversion of the resting form to the activated form. The results provide functional support for the previous structural model, identify the specific effect of phosphorylation on the enzyme, and rationalize the lack of change in the protein structure upon phosphorylationthe major conclusions.
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影响因子：
6.8
作者：
Fitzpatrick, Paul F.
通讯作者：
Fitzpatrick, Paul F.
DOI：
10.1073/pnas.1516967113
发表时间：
2016-03-01
影响因子：
11.1
作者：
Arturo, Emilia C.;Gupta, Kushol;Jaffe, Eileen K.
通讯作者：
Jaffe, Eileen K.
影响因子：
2.9
作者：
Roberts, Kenneth M.;Khan, Crystal A.;Hinck, Cynthia S.;Fitzpatrick, Paul F.
通讯作者：
Fitzpatrick, Paul F.
DOI：
10.1073/pnas.92.11.4743
发表时间：
1995-05-23
影响因子：
11.1
作者：
KOWLESSUR, D;YANG, XJ;KAUFMAN, S
通讯作者：
KAUFMAN, S
影响因子：
2.9
作者：
Johnson, Kenneth A.;Simpson, Zachary B.;Blom, Thomas
通讯作者：
Blom, Thomas