Characterization of the major protein-tyrosine-phosphatases of human placenta.
Characterization of the major protein-tyrosine-phosphatases of human placenta.
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DOI：
10.1016/s0021-9258(18)68703-4
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发表时间：
1988-05
期刊：
影响因子：
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通讯作者：
N. Tonks;C. D. Diltz;E. Fischer
中科院分区：
文献类型：
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作者：
N. Tonks;C. D. Diltz;E. Fischer
在前一篇文章（Tonks, N. K.、Diltz, C. D. 和 Fischer, E. H. (1988) J. Biol. Chem. 263, 6722-6730）中，描述了从人胎盘中纯化主要蛋白酪氨酸磷酸酶，其中一些具有明显的同质性。该报告比较了这些酶的特征，并清楚地鉴定了至少两种不同的蛋白质酪氨酸磷酸酶催化亚基。所有这些都对磷酸酪氨酰残基绝对具有特异性，并且对任何测试的含磷酸丝氨酰/磷酸苏氨酰的蛋白质均没有活性；它们对底物表现出高亲和力，Km 值在亚微摩尔范围内。所有这些都绝对依赖于巯基化合物，并且似乎含有至少一个对于活性至关重要的高反应性半胱氨酰残基。亚型 1A 和 1B 可以通过它们对聚阴离子和聚阳离子化合物的反应来区分。 1B 酶被 EDTA、精胺、亚精胺和髓磷脂碱性蛋白激活的程度比 1A 亚型更大。此外，与 1A 亚型相比，它们被浓度低约 2 个数量级的肝素（IC50 约为 20 nM）和 1:1 或 4:1 聚（谷氨酸/酪氨酸）（IC50 约为 50 nM）所抑制。令人惊讶的是，谷氨酸/酪氨酸共聚物的抑制是严格非竞争性的。用无色杆菌蛋白酶 I 或金黄色葡萄球菌 V8 蛋白酶消化后的肽图谱支持这样的观点：虽然蛋白质酪氨酸磷酸酶亚型 1A 和 1B 不同，但它们的可溶性和颗粒对应物在结构上密切相关，并且与丝氨酸/苏氨酸磷酸酶 1 和 2A 不同。
In the preceding article (Tonks, N. K., Diltz, C. D., and Fischer, E. H. (1988) J. Biol. Chem. 263, 6722-6730), the purification of the major protein-tyrosine-phosphatases from human placenta, some to apparent homogeneity, was described. This report compares the characteristics of these enzymes and clearly identifies at least two distinct protein-tyrosine-phosphatase catalytic subunits. All were absolutely specific for phosphotyrosyl residues and showed no activity on any of the phosphoseryl/phosphothreonyl-containing proteins tested; they exhibited a high affinity for substrate with Km values in the submicromolar range. All were absolutely dependent on sulfhydryl compounds and appeared to contain at least one highly reactive cysteinyl residue essential for activity. Subtypes 1A and 1B could be distinguished by their response to polyanionic and polycationic compounds. The 1B enzymes were activated by EDTA, spermine, spermidine, and myelin basic protein to a greater extent than the 1A subtypes. Furthermore, they were inhibited by approximately 2 orders of magnitude lower concentrations of heparin (IC50 approximately 20 nM) and 1:1 or 4:1 poly (glutamate/tyrosine) (IC50 approximately 50 nM) than the 1A subtypes. Surprisingly, inhibition by the glutamate/tyrosine copolymers was strictly noncompetitive. Peptide mapping following digestion with Achromobacter protease I or Staphylococcus aureus V8 protease supported the view that, whereas protein-tyrosine-phosphatase subtypes 1A and 1B are different, their soluble and particulate counterparts are closely related structurally and are distinct from serine/threonine phosphatases 1 and 2A.