Mishiro Emi, Sakakibara Yoichi, Liu Ming-Cheh, Suiko Masahito
Department of Biochemistry and Applied Biosciences, Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192.
J Biochem. 2006 Nov;140(5):731-7. doi: 10.1093/jb/mvj206. Epub 2006 Oct 8.
Protein tyrosine sulfation is emerging as a widespread post-translational modification in multicellular eukaryotes. The responsible enzyme, named tyrosylprotein sulfotransferase (TPST), catalyzes the sulfate transfer from 3'-phosphoadenosine 5'-phosphosulfate to tyrosine residues of proteins. Two distinct TPSTs, designated TPST-1 and TPST-2, had previously been identified. In the present study, we cloned human TPST-1 and TPST-2 expressed and characterized the recombinant enzymes using peptide substrates. These enzymes displayed distinct acidic pH optima and stimulatory effects of Mn(2+). Additionally, the activity of TPST-2, but not TPST-1, was stimulated in the presence of Mg(2+). Compared with TPST-2, TPST-1 displayed considerably lower K(m) and V(max) for the majority of the tested peptide substrates, implying their differential substrate specificity. Quantitative real-time PCR analysis showed that although the two TPSTs were co-expressed in all 20 human tissues examined, the levels of expression of TPST-1 and TPST-2 varied significantly among different tissues. These latter findings may imply distinct physiological functions of TPST-1 and TPST-2.
蛋白质酪氨酸硫酸化正逐渐成为多细胞真核生物中一种广泛存在的翻译后修饰。负责该修饰的酶名为酪蛋白硫酸转移酶（TPST），它催化硫酸根从3'-磷酸腺苷5'-磷酸硫酸转移至蛋白质的酪氨酸残基上。此前已鉴定出两种不同的TPST，分别命名为TPST-1和TPST-2。在本研究中，我们克隆了人TPST-1和TPST-2，并使用肽底物对重组酶进行了表达和特性分析。这些酶表现出不同的酸性最适pH值以及锰离子（Mn(2+)）的刺激作用。此外，在镁离子（Mg(2+)）存在的情况下，TPST-2的活性受到刺激，而TPST-1则不受影响。与TPST-2相比，TPST-1对大多数测试肽底物的米氏常数（K(m)）和最大反应速度（V(max)）要低得多，这意味着它们具有不同的底物特异性。定量实时PCR分析表明，尽管这两种TPST在所有检测的20种人体组织中均共同表达，但TPST-1和TPST-2的表达水平在不同组织中存在显著差异。这些结果可能暗示TPST-1和TPST-2具有不同的生理功能。
