亞硫酸基轉移□之定位與功能分析

Abstract

亞硫酸基轉移□參與許多重要生理反應，如藥物代謝、類固醇與荷爾蒙調控、調節神經傳導物質功能和癌化過程。在亞硫酸基化反應中，磷酸腺□酸磷□硫酸鹽 (PAPS) 為亞硫酸基的來源，其受質可廣泛的包含醣類ぶ蛋白質ぶ多種內生性小分子及環境荷爾蒙等。 為了進一步探討亞硫酸基轉移□在生物體中可能的生理與功能意義，本研究利用兩種重要的動物模型，果蠅及斑馬魚，作為亞硫酸基轉移□之定位與功能分析之平台。首先，研究結果顯示在果蠅全腦中，類脫氫表雄甾酮亞硫酸基轉移□之蛋白質 (DHEA ST-like protein) 選擇性地表現在果蠅腦中特殊的神經細胞及神經纖維，推測可能和記憶與學習迴路相關。在斑馬魚中，有兩種新的亞硫酸基轉移□被確認。此兩種□針對環境荷爾蒙，特別是羥化多氯化聯苯 (hydroxylated PCB) 有最強的亞硫酸基化能力，在斑馬魚的胚胎形成與發育過程中，此兩種□大量表現在幼魚時期，推測在斑馬魚器官發育之初期，魚體已具有代謝環境荷爾蒙的能力。另外，本研究發展出一個針對酪胺酸亞硫酸基化之偵測方法，並發現三個恆常性血液蛋白有酪胺酸亞硫酸基化的現象。結果顯示，以果蠅及斑馬魚為平台，本研究詳細地探討亞硫酸基轉移□之定位與功能分析，期能為日後之研究提供可用之相關資訊。

Sulfotransferases (SULTs) constitute a superfamily of related enzymes that play important roles in the regulation of detoxification, steroid hormone action, neurotransmitter function, drug metabolism, and carcinogenesis. Sulfation, catalyzed by SULTs, is the critical biotransformation process for transferring a sulfuryl group from the cofactor 3’-phosphoadenosine-5’-phophosulfate (PAPS) to a wide range of structurally diverse endogenous and xenobiotic compounds. It is believed that understanding the expression pattern and cellular distribution of SULTs, along with the functional and structural information, will assist in determining the physical and functional significance of SULTs. Here we utilized two ideal animal models, fruit fly (Drosophila melanogaster) and zebrafish (Danio rerio), as the alternative testing systems for investigating the localization and functional significance of SULTs. Firstly, a systematical analysis demonstrated that dehydroepiandrosterone sulfotransferase-like protein was expressed in fruit fly, which so far has no evidence indicating the presence of cytosolic SULTs, and was abundant in the specific neural bodies as well as in several bundles of synapses in fruit fly neuronal circuits. Secondly, two novel cytosolic SULTs, SULT1 ST7 and SULT1 ST8, were identified and characterized in zebrafish. They both exhibited strong sulfating activities toward environmental estrogens, particularly hydroxylated polychlorinated biphenyls (PCBs), among various endogenous and xenobiotic compounds tested as substrates. Developmental expression experiments also revealed distinct expression patterns of SULT1 ST7 and ST8 during embryonic development and throughout the larval stage onto maturity. Lastly, to better understand the functional regulation of SULTs, a target-specific approach for the identification of tyrosine sulfation had been established. Three new tyrosine-sulfated hemostatic proteins were identified. Such a target-specific approach will allow for investigation of sulfated-tyrosine proteins of other biochemical/physiological pathways/processes and contribute to a better understating of post-translational modification by tyrosine sulfation.