Hochman Y, Zakim D
J Biol Chem. 1983 Oct 10;258(19):11758-62.
UDP-glucuronyltransferase (EC 2.4.1.17) in intact, untreated microsomes from pig liver is activated by relatively low concentrations of UDP-N-acetylglucosamine. This property is absent after treatment of microsomes with detergents or phospholipases, and also is not a characteristic of pure, delipidated enzyme. Sensitivity to activation by UDP-N-acetylglucosamine was reconstituted, however, by incorporation of pure, delipidated enzyme into unilamellar bilayers of phosphatidylcholine that were in a gel phase. Warming of these bilayers to just above the temperature for the gel to liquid crystalline phase transition led to an abrupt loss of sensitivity of UDP-glucuronyltransferase to activation by UDP-N-acetylglucosamine. These experiments establish that sensitivity to activation by UDP-N-acetylglucosamine is an inherent property of UDP-glucuronyltransferase. The data also suggest that the lipid environment of UDP-glucuronyltransferase in intact, untreated microsomes can modulate the sensitivity of this enzyme to allosteric activation by UDP-N-acetylglucosamine, and that this lipid environment is in a gel phase in intact microsomes at 37 degrees C.
猪肝脏完整、未处理的微粒体中的UDP-葡萄糖醛酸基转移酶（EC 2.4.1.17）可被相对低浓度的UDP-N-乙酰葡糖胺激活。在用去污剂或磷脂酶处理微粒体后，此特性消失，并且它也不是纯的、脱脂酶的特征。然而，通过将纯的、脱脂酶掺入处于凝胶相的磷脂酰胆碱单层双分子层中，可重建对UDP-N-乙酰葡糖胺激活的敏感性。将这些双分子层加热至略高于凝胶向液晶相转变的温度会导致UDP-葡萄糖醛酸基转移酶对UDP-N-乙酰葡糖胺激活的敏感性突然丧失。这些实验证实对UDP-N-乙酰葡糖胺激活的敏感性是UDP-葡萄糖醛酸基转移酶的固有特性。数据还表明，完整、未处理的微粒体中UDP-葡萄糖醛酸基转移酶的脂质环境可调节该酶对UDP-N-乙酰葡糖胺别构激活的敏感性，并且在37℃时完整微粒体中的这种脂质环境处于凝胶相。
