Gruppuso P A, Boylan J M, Smiley B L, Fallon R J, Brautigan D L
Department of Pediatrics, Rhode Island Hospital, Providence 02903.
Biochem J. 1991 Mar 1;274 ( Pt 2)(Pt 2):361-7. doi: 10.1042/bj2740361.
Regulation of cell growth and metabolism by protein tyrosine phosphorylation involves dephosphorylation via the action of protein tyrosine phosphatases (PTPases). We have characterized the membrane PTPases in rat liver, monitoring their activity by measuring the dephosphorylation of P-Tyr-reduced, carboxyamidomethylated and maleylated lysozyme (P-Tyr-RCML) and P-Tyr-myelin basic protein (P-Tyr-MBP). Separation of membrane PTPases by poly (L-lysine) chromatography yielded three peaks of PTPase, termed I, II and III. PTPases I and II were most active with P-Tyr-RCML, whereas PTPase III showed greater activity with P-Tyr-MBP than with P-Tyr-RCML (ratio of activities 4:1). Separation of membrane proteins by gel-filtration chromatography yielded two peaks of activity. Based on substrate specificity, sensitivity to inhibitors and requirement for thiol-containing compounds, the activity peak with an Mr of approximately 400,000 corresponded to PTPase III, whereas that with an Mr of approx. 40,000 contained PTPases I and II. All three PTPases dephosphorylated epidermal growth factor receptors and insulin receptors, but only PTPases I and II were active with P-Tyr-asialoglycoprotein receptors. Although none of the above characteristics distinguished between PTPases I and II, only PTPase I reacted in a Western immunoblotting procedure with anti-peptide antibodies directed towards human placental PTPase. We conclude that the membrane fraction from rat liver contains at least three distinct PTPases.
蛋白质酪氨酸磷酸化对细胞生长和代谢的调节涉及通过蛋白质酪氨酸磷酸酶（PTPases）的作用进行去磷酸化。我们已经对大鼠肝脏中的膜PTPases进行了表征，通过测量P-酪氨酸还原、羧酰胺甲基化和马来酰化溶菌酶（P-Tyr-RCML）以及P-酪氨酸髓鞘碱性蛋白（P-Tyr-MBP）的去磷酸化来监测它们的活性。通过聚（L-赖氨酸）色谱法分离膜PTPases产生了三个PTPase峰，分别称为I、II和III。PTPases I和II对P-Tyr-RCML的活性最高，而PTPase III对P-Tyr-MBP的活性比对P-Tyr-RCML的活性更高（活性比为4:1）。通过凝胶过滤色谱法分离膜蛋白产生了两个活性峰。根据底物特异性、对抑制剂的敏感性以及对含硫醇化合物的需求，Mr约为400,000的活性峰对应于PTPase III，而Mr约为40,000的活性峰包含PTPases I和II。所有三种PTPases都能使表皮生长因子受体和胰岛素受体去磷酸化，但只有PTPases I和II对P-酪氨酸去唾液酸糖蛋白受体有活性。尽管上述特征都无法区分PTPases I和II，但只有PTPase I在Western免疫印迹实验中与针对人胎盘PTPase的抗肽抗体发生反应。我们得出结论，大鼠肝脏的膜部分至少含有三种不同的PTPases。
