Pinna L A, Donella A, Clari G, Moret V
Biochim Biophys Acta. 1975 Aug 26;397(2):519-28. doi: 10.1016/0005-2744(75)90142-4.
Some structural features required for the enzymatic phosphorylation of phosvitin by purified rat liver cytosol phosvitin kinase have been investigated by testing the activity of such an enzyme toward phosphopeptides differing in size and chemical composition, obtained by pronase or acid hydrolysis of phosvitin. The results obtained can be summarized as follows: (a) Phosvitin kinase phosphorylates even fairly simple phosphopeptides (mol.wt 1000-2000) at rates comparable with intact phosvitin. (b) Acetylation of both phosvitin and pronase phosphopeptides completely prevents their phosphorylation indicating that some lysine residues are strictly required for the phosvitin kinase reaction. (c) Accordingly polyphosphorylserine blocks Ser(P)n which are very actively phosphorylated in phosvitin and pronase phosphopeptides, do not undergo any more enzymatic phosphorylation once isolated as such in a form free of other amino acids. (d) The activity of phosvitin kinase toward substrates probably devoid of Ser(P)n blocks suggests that there are not required for the protein kinase reaction. However, they apparently enhance the phosphorylation rate of the peptide substrates, likely by making easier their binding to the enzyme. It is proposed therefore that the peptidic unit able to undergo phosphorylation by rat liver cytosol phosvitin kinase consists of one or more phosphorylserine residues having in their close proximity a lysine residue playing a critical role in the mechanism of transphosphorylation.
通过测试纯化的大鼠肝细胞溶质磷蛋白激酶对经链霉蛋白酶或酸水解磷蛋白得到的、大小和化学组成不同的磷酸肽的活性，研究了磷蛋白酶促磷酸化所需的一些结构特征。所得结果可总结如下：(a) 磷蛋白激酶对相当简单的磷酸肽（分子量1000 - 2000）进行磷酸化的速率与完整磷蛋白相当。(b) 磷蛋白和链霉蛋白酶磷酸肽的乙酰化完全阻止了它们的磷酸化，表明磷蛋白激酶反应严格需要一些赖氨酸残基。(c) 相应地，多聚磷酸丝氨酸会阻断磷蛋白和链霉蛋白酶磷酸肽中非常容易被磷酸化的Ser(P)n，一旦以不含其他氨基酸的形式分离出来，就不再进行任何酶促磷酸化。(d) 磷蛋白激酶对可能不含Ser(P)n阻断的底物的活性表明，蛋白激酶反应不需要它们。然而，它们显然提高了肽底物的磷酸化速率，可能是通过使它们更容易与酶结合。因此，有人提出，能够被大鼠肝细胞溶质磷蛋白激酶磷酸化的肽单元由一个或多个磷酸丝氨酸残基组成，在它们的紧邻位置有一个赖氨酸残基，该赖氨酸残基在转磷酸化机制中起关键作用。
