Shaw J M, Pieringer R A
J Biol Chem. 1977 Jun 25;252(12):4391-4.
The biosynthesis of glucuronosyl diacylglycerol from UDP-glucuronate and diacylglycerol is catalyzed by an enzyme found in both the 34,800 X g supernatant and particulate preparations from disrupted Pseudomonas diminuta (ATCC 11586). UDP-glucuronate served as the glucuronosyl donor and could not be replaced by glucuronic acid, glucuronate-1-phosphate, and a number of nucleotide-linked sugars. The maximum velocity was estimated to be 19 nmol of glucuronosyl diacylglycerol synthesized/h/mg of protein in the presence of the 34,800 X g particulate enzyme and 63 nmol/h/mg of protein with the 34,800 X g supernatant preparation. The apparent Km for UDP-glucuronate was 4.2 micronM for supernatant and 4.4 to 6.0 micronM for particulate preparations. The biosynthesis of glucuronosyl diacylglycerol in vitro, was strongly dependent upon exogenous diacylglycerols containing unsaturated and shorter chain fatty acids. The enzymatic activity was very heat-labile and lost about 80% of the initial rate of synthesis after preincubation for 5 min at 37 degrees. The reaction was stimulated by 14.7 mM Triton X-100 and had an optimal pH of 7.1 and an ionic strength of 0.2 M. Divalent cations were not required.
由UDP - 葡萄糖醛酸和二酰基甘油生物合成葡糖醛酸基二酰基甘油，是由一种在34,800×g离心的上清液以及来自短小假单胞菌（ATCC 11586）破碎细胞的颗粒制剂中均能找到的酶催化的。UDP - 葡萄糖醛酸作为葡糖醛酸基供体，不能被葡萄糖醛酸、葡萄糖醛酸 - 1 - 磷酸以及多种核苷酸连接的糖所替代。在存在34,800×g颗粒酶的情况下，最大反应速度估计为每小时每毫克蛋白质合成19 nmol葡糖醛酸基二酰基甘油，而对于34,800×g上清液制剂，该速度为每小时每毫克蛋白质63 nmol。UDP - 葡萄糖醛酸的表观Km值，上清液为4.2 μM，颗粒制剂为4.4至6.0 μM。体外合成葡糖醛酸基二酰基甘油强烈依赖于含有不饱和及较短链脂肪酸的外源性二酰基甘油。该酶活性对热非常不稳定，在37℃预孵育5分钟后，初始合成速率损失约80%。该反应受到14.7 mM Triton X - 100的刺激，最佳pH值为7.1，离子强度为0.2 M。不需要二价阳离子。
