Smith P F
J Bacteriol. 1971 Dec;108(3):986-91. doi: 10.1128/jb.108.3.986-991.1971.
The biosynthesis of cholesteryl glucoside by Mycoplasma gallinarum strain J proceeds by the transfer of glucose from uridine-5'-diphosphoglucose to membrane-bound sterol. Galactose also can be coupled to cholesterol via uridine-5'-diphosphogalactose. The reaction is specific for the uridine-5'-diphospho sugars. Enzymatic activity is associated with the membrane. Treatment of the membrane to remove endogenous sterol inactivates the enzyme. Only sterol which has been bound to the membrane participates in the reaction. The optimum pH is about 8.0, and Mg(2+) is required. The reaction is unaffected by nucleotide triphosphate, uridine-5'-monophosphate, and uridine-5'-diphosphate. Reduction of pH to the optimum for beta-glucosidase in the membrane results in loss of synthesized glucoside. The enzyme is saturated at 0.5 mm uridine-5'-diphosphoglucose. The apparent K(m) of 2.05 x 10(-7) indicates a high affinity of the enzyme for the nucleotide sugar.
鸡支原体J株合成胆固醇葡萄糖苷的过程是将葡萄糖从尿苷-5'-二磷酸葡萄糖转移至膜结合固醇。半乳糖也可通过尿苷-5'-二磷酸半乳糖与胆固醇偶联。该反应对尿苷-5'-二磷酸糖具有特异性。酶活性与膜相关。处理膜以去除内源性固醇会使酶失活。只有与膜结合的固醇参与反应。最适pH约为8.0，且需要Mg(2+)。该反应不受三磷酸核苷酸、尿苷-5'-单磷酸和尿苷-5'-二磷酸的影响。将pH降至膜中β-葡萄糖苷酶的最适值会导致合成的葡萄糖苷丢失。该酶在0.5 mM尿苷-5'-二磷酸葡萄糖时饱和。表观K(m)为2.05×10(-7)表明该酶对核苷酸糖具有高亲和力。
