Biosynthesis of beta-glucuronides of retinol and of retinoic acid in vivo and in vitro.
Biosynthesis of beta-glucuronides of retinol and of retinoic acid in vivo and in vitro.
复制标题
视黄醇和视黄酸的β-葡萄糖苷酸的体内和体外生物合成。
作者：
K. Lippel;J. Olson
大鼠门静脉注射视黄醇-6，7-(14)C后，胆汁中出现视黄醇的O-乙醚衍生物--视黄酸葡萄糖苷酸酯。洗涤后的大鼠肝微粒体分别与尿苷二磷葡萄糖醛酸(UDPGA)、维甲酸或视黄醇孵育后，也可在体外合成维甲酸葡萄糖醛酸脂和维甲酸葡萄糖苷酸酯。肾的微粒体和肠粘膜的颗粒部分也证明了维甲酰-葡萄糖醛酸苷的合成。通过其紫外吸收光谱、对紫外光或荧光的猝灭、其在两种溶剂体系中的薄层层析行为以及对其副葡萄糖醛酸苷酶降解产物的鉴定，对其进行了表征。以维甲酸为底物，大鼠肝微粒体UDP葡萄糖醛酸基转移酶的最适pH为7.0，最适温度为38℃，与维甲酸和UDPGA的浓度有明显的依赖关系，但不受一些可能的抑制剂、保护剂和竞争底物的影响。在牛视网膜的整个匀浆、细胞组分或外节中未检测到视网膜向维甲酸的转化和由维甲酸合成视黄酸葡萄糖醛酸脂。
After the intraportal injection of retinol-6,7-(14)C to rats, the O-ether derivative of retinol, retinyl -glucosiduronate, appears in the bile. Both retinoyl -glucuronide and retinyl -glucosiduronate are also synthesized in vitro when washed rat liver microsomes are incubated with uridine diphosphoglucuronic acid (UDPGA) and either retinoic acid or retinol, respectively. The synthesis of retinoyl -glucuronide was also demonstrated in microsomes of the kidney and in particulate fractions of the intestinal mucosa. The glucuronides were characterized by their UV absorption spectra, by their quenching of UV light or fluorescence under it, by their thin-layer chromatographic behavior in two solvent systems, and by the identification of products released during their hydrolysis by -glucuronidase. With retinoic acid as the substrate, the UDP glucuronyl transferase of rat liver microsomes had a pH optimum of 7.0, a temperature optimum of 38 degrees C, and a marked dependence on the concentrations of both retinoic acid and UDPGA, but was unaffected by a number of possible inhibitors, protective agents, and competitive substrates. The conversion of retinal to retinoic acid and the synthesis of retinoyl -glucuronide from retinoic acid could not be detected in whole homogenates, cell fractions, or outer segments of the bovine retina.