Zakim D, Vessey D A
J Biol Chem. 1975 Jan 10;250(1):342-3.
UDP-glucose, UDP-mannose, and UDP-xylose inhibit microsomal UDP-glucuronyltransferase in assays at 6 degrees. None of these compounds affects activity in assays at 37 degrees. Studies with UDP-glucose revealed an abrupt temperature-dependent change in the effect of this compound on the activity of UDP-glucuronyltransferase. Inhibition by UDP-glucose was observed only at temperatures below 16 degrees. UDP-glucose had no effect on activity in assays at temperatures of 16 degrees and above. UDP-N-acetylglucosamine activates UDP-glucuronyltransferase at temperatures at or above 16 degrees, but has no effect on activity below 16 degrees. The lipid portion of the microsomal membrane is known to undergo a phase change at 16 degrees. These data indicate, therefore, that significant alterations in the regulatory properties of UDP-glucuronyltransferase are associated with temperature-induced phase separations within the lipid portion of the microsomal membrane.
在6摄氏度的测定中，UDP - 葡萄糖、UDP - 甘露糖和UDP - 木糖会抑制微粒体UDP - 葡萄糖醛酸基转移酶。这些化合物在37摄氏度的测定中均不影响酶活性。对UDP - 葡萄糖的研究表明，该化合物对UDP - 葡萄糖醛酸基转移酶活性的影响存在突然的温度依赖性变化。仅在低于16摄氏度的温度下观察到UDP - 葡萄糖的抑制作用。在16摄氏度及以上的温度下，UDP - 葡萄糖对测定中的酶活性没有影响。UDP - N - 乙酰葡糖胺在16摄氏度及以上的温度下激活UDP - 葡萄糖醛酸基转移酶，但在低于16摄氏度时对酶活性没有影响。已知微粒体膜的脂质部分在16摄氏度时会发生相变。因此，这些数据表明，UDP - 葡萄糖醛酸基转移酶调节特性的显著改变与微粒体膜脂质部分温度诱导的相分离有关。
