Chowdhury J R, Chowdhury N R, Moscioni A D, Tukey R, Tephly T, Arias I M
Biochim Biophys Acta. 1983 Nov 22;761(1):58-65. doi: 10.1016/0304-4165(83)90362-8.
Hepatic uridinediphosphoglucuronate glucuronosyl transferase (UDPglucuronyltransferase, EC 2.4.1.17) is functionally heterogeneous; 4-nitrophenol and bilirubin are representative substrates for two functional forms of the enzyme. UDPglucuronyltransferase activity for bilirubin and 4-nitrophenol was separated from solubilized rat liver microsomes by DEAE-cellulose chromatography and corresponding enzymes were purified. A radioimmunoassay was developed using a rabbit antiserum against purified rat 4-nitrophenol-specific UDPglucuronyltransferase, which precipitated enzyme activities toward both 4-nitrophenol and bilirubin. After treatment with triiodothyronine (T3) (0.55 mg/kg body weight), hepatic microsomal UDPglucuronyltransferase activity for 4-nitrophenol was increased 400% as compared to controls; the enzyme activity for bilirubin was decreased by 80%; the changes in the substrate-specific enzyme activities were reflected in the enzymatically active fractions separated after DEAE-cellulose chromatography. The changes in enzyme activities paralleled changes in the concentrations of the two corresponding UDP glucuronyltransferase proteins in the chromatographic fractions, as measured by radioimmunoassay. The results indicate that the opposite effects of T3 on the two forms of UDPglucuronyltransferase activity is due to its differential effect on corresponding enzyme proteins.
肝脏尿苷二磷酸葡萄糖醛酸葡萄糖醛酸基转移酶（UDP葡萄糖醛酸基转移酶，EC 2.4.1.17）在功能上具有异质性；4-硝基苯酚和胆红素是该酶两种功能形式的代表性底物。通过DEAE-纤维素色谱法从溶解的大鼠肝脏微粒体中分离出胆红素和4-硝基苯酚的UDP葡萄糖醛酸基转移酶活性，并对相应的酶进行了纯化。使用针对纯化的大鼠4-硝基苯酚特异性UDP葡萄糖醛酸基转移酶的兔抗血清开发了一种放射免疫测定法，该抗血清沉淀了针对4-硝基苯酚和胆红素的酶活性。用三碘甲状腺原氨酸（T3）（0.55mg/kg体重）处理后，与对照组相比，肝脏微粒体中4-硝基苯酚的UDP葡萄糖醛酸基转移酶活性增加了400%；胆红素的酶活性降低了80%；底物特异性酶活性的变化反映在DEAE-纤维素色谱法分离后的酶活性组分中。通过放射免疫测定法测量，酶活性的变化与色谱组分中两种相应UDP葡萄糖醛酸基转移酶蛋白浓度的变化平行。结果表明，T3对两种形式的UDP葡萄糖醛酸基转移酶活性的相反作用是由于其对相应酶蛋白的不同作用。
