Substrate specificity of IphP, a cyanobacterial dual-specificity protein phosphatase with MAP kinase phosphatase activity.
Substrate specificity of IphP, a cyanobacterial dual-specificity protein phosphatase with MAP kinase phosphatase activity.
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IphP 的底物特异性，IphP 是一种具有 MAP 激酶磷酸酶活性的蓝藻双特异性蛋白磷酸酶。
DOI：
10.1021/bi9600409
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Kennelly,PJ
中科院分区：
文献类型：
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作者：
Howell,LD;Griffiths,C;Slade,LW;Potts,M;Kennelly,PJ
蓝藻双特异性蛋白磷酸酶，IphP，底物特异性进行了探讨，使用各种潜在的底物。该酶显示磷酸单酯酶活性对广泛的肽，蛋白质，和低分子量的有机磷酸酯化合物。它对磷酸二酯、磷酰胺、羧基酯或磺基酯显示出很少或没有水解酶活性。然而，它确实显示出可测量的焦磷酸酶活性，特别是对ADP和ATP。在低分子量的磷酸单酯中，作为离去基团醇的一部分或与其紧邻的芳环的存在，如在5 '-AMP中，是水解的强阳性决定因素。在肽和蛋白质底物中，注意到电荷特征和水解之间的粗糙但不完美的相关性，其中蛋白质和酸性性质的磷酸化位点似乎是有利的。肝素以底物依赖性方式影响IphP活性。对于小分子有机磷，肝素没有显着影响，但对大多数蛋白质和肽底物有抑制作用。然而，对磷酸丝氨酰酪蛋白和MAP激酶，它的活性增强多达10倍。这种增强归因于肝素结合这些底物蛋白以及IphP并将它们招募到相同微环境的能力。
The substrate specificity of the cyanobacterial dual-specificity protein phosphatase, IphP, was explored using a variety of potential substrates. The enzyme displayed phosphomonoesterase activity toward a broad range of peptide, protein, and low molecular weight organophosphate compounds. It displayed little or no hydrolase activity toward phosphodiesters, phosphoramides, carboxyl esters, or sulfoesters. However, it did display measurable pyrophosphatase activity, especially toward ADP and ATP. Among the low molecular weight phosphomonoesters, the presence of an aromatic ring either as part of the leaving group alcohol or immediately adjacent thereto, as in 5‘-AMP, was a strong positive determinant for hydrolysis. Among peptide and protein substrates, a rough, but imperfect, correlation between charge character and hydrolysis was noted in which proteins and phosphorylation sites of an acidic nature seemed favored. Heparin affected IphP activity in a substrate-dependent manner. Toward small organophosphates, heparin had no significant effect, but it was inhibitory toward most protein and peptide substrates. However, toward phosphoseryl casein and MAP kinase, it enhanced activity as much as 10-fold. This enhancement was attributed to the ability of heparin to bind to these substrate proteins, as well as IphP, and recruit them to the same microenvironment.