Arylsulfatase G, a novel lysosomal sulfatase
Arylsulfatase G, a novel lysosomal sulfatase
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DOI：
10.1074/jbc.m709917200
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发表时间：
2008-04-25
影响因子：
4.8
通讯作者：
Dierks, Thomas
中科院分区：
文献类型：
--
作者：
Frese, Marc-Andre;Schulz, Stefanie;Dierks, Thomas
硫酸酯酶是一个保守的酶家族，能特异性水解多种底物如糖胺聚糖、类固醇硫酸酯或硫脂中的硫酸酯。通过修饰其底物的硫酸化状态，硫酸酯酶在生理过程的控制中发挥关键作用，包括细胞降解、细胞信号传导和激素调节。硫酸酯酶活性的丧失与各种严重的病理生理学状况有关，如溶酶体贮积症、发育异常或癌症。该家族的一个新成员芳基硫酸酯酶G（ASG）最初被描述为缺乏体外芳基硫酸酯酶活性并定位于内质网的酶。与这些结果相反，我们在这里证明，ASG确实对不同的假底物，如对硝基儿茶酚硫酸酯和4-甲基伞形酮硫酸酯具有芳基硫酸酯酶活性。ASG的活性取决于Cys-84残基，预计Cys-84残基将在脱乙酰后转化为关键活性位点C-α-甲酰甘氨酸。磷酸盐是一种强的竞争性ASG抑制剂。ASG作为未加工的63-kDa单体是有活性的，并且显示出典型地见于溶酶体硫酸酯酶的酸性pH最佳值。在转染的细胞中，ASG在溶酶体内积累，如间接免疫荧光显微镜所示。此外，ASG是特异性结合甘露糖6-磷酸受体的糖蛋白，证实了其溶酶体定位。发现ARSG mRNA表达具有组织特异性，在肝脏、肾脏和胰腺中表达最高，表明ASG的代谢作用可能与迄今未分类的溶酶体贮积症相关。
The sulfatases constitute a conserved family of enzymes that specifically hydrolyze sulfate esters in a wide variety of substrates such as glycosaminoglycans, steroid sulfates, or sulfolipids. By modifying the sulfation state of their substrates, sulfatases play a key role in the control of physiological processes, including cellular degradation, cell signaling, and hormone regulation. The loss of sulfatase activity has been linked with various severe pathophysiological conditions such as lysosomal storage disorders, developmental abnormalities, or cancer. A novel member of this family, arylsulfatase G (ASG), was initially described as an enzyme lacking in vitro arylsulfatase activity and localizing to the endoplasmic reticulum. Contrary to these results, we demonstrate here that ASG does indeed have arylsulfatase activity toward different pseudosubstrates like p-nitrocatechol sulfate and 4-methylumbelliferyl sulfate. The activity of ASG depends on the Cys-84 residue that is predicted to be post-translationally converted to the critical active site C-alpha-formylglycine. Phosphate acts as a strong, competitive ASG inhibitor. ASG is active as an unprocessed 63-kDa monomer and shows an acidic pH optimum as typically seen for lysosomal sulfatases. In transfected cells, ASG accumulates within lysosomes as indicated by indirect immunofluorescence microscopy. Furthermore, ASG is a glycoprotein that binds specifically to mannose 6-phosphate receptors, corroborating its lysosomal localization. ARSG mRNA expression was found to be tissue-specific with highest expression in liver, kidney, and pancreas, suggesting a metabolic role of ASG that might be associated with a so far non-classified lysosomal storage disorder.